Interference management utilizing power and attenuation profiles

ABSTRACT

Interference that occurs during wireless communication may be managed through the use of fractional reuse and other techniques. In some aspects fractional reuse may relate to HARQ interlaces, portions of a timeslot, frequency spectrum, and spreading codes. Interference may be managed through the use of a transmit power profile and/or an attenuation profile. Interference also may be managed through the use of power management-related techniques.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

This application claims the benefit of and priority to commonly ownedU.S. Provisional Patent Application No. 60/974,428, filed Sep. 21, 2007,U.S. Provisional Patent Application No. 60/974,449, filed Sep. 21, 2007,U.S. Provisional Patent Application No. 60/974,794, filed Sep. 24, 2007,and U.S. Provisional Patent Application No. 60/977,294, filed Oct. 3,2007, the disclosure of each of which is hereby incorporated byreference herein.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to concurrently filed and commonly ownedU.S. patent application Ser. No. 12/212,622, entitled “INTERFERENCEMANAGEMENT UTILIZING HARQ INTERLACES,” ; U.S. patent application Ser.No. 12/212,638, entitled “INTERFERENCE MANAGEMENT EMPLOYING FRACTIONALTIME REUSE,” ; U.S. patent application Ser. No. 12/212,465, entitled“INTERFERENCE MANAGEMENT UTILIZING POWER CONTROL,” ; U.S. patentapplication Ser. No. 12/212,513, entitled “INTERFERENCE MANAGEMENTEMPLOYING FRACTIONAL FREQUENCY REUSE,” ; and U.S. patent applicationSer. No. 12/212,570, entitled “INTERFERENCE MANAGEMENT EMPLOYINGFRACTIONAL CODE REUSE,” ; the disclosure of each of which is herebyincorporated by reference herein.

BACKGROUND

1. Field

This application relates generally to wireless communication and morespecifically, but not exclusively, to improving communicationperformance.

2. Introduction

Wireless communication systems are widely deployed to provide varioustypes of communication (e.g., voice, data, multimedia services, etc.) tomultiple users. As the demand for high-rate and multimedia data servicesrapidly grows, there lies a challenge to implement efficient and robustcommunication systems with enhanced performance.

To supplement conventional mobile phone network base stations,small-coverage base stations may be deployed (e.g., installed in auser's home) to provide more robust indoor wireless coverage to mobileunits. Such small-coverage base stations are generally known as accesspoint base stations, Home NodeBs, or femto cells. Typically, suchsmall-coverage base stations are connected to the Internet and themobile operator's network via a DSL router or a cable modem.

Since radio frequency (“RF”) coverage of small-coverage base stationsmay not be optimized by the mobile operator and deployment of such basestations may be ad-hoc, RF interference issues may arise. Moreover, softhandover may not be supported for small-coverage base stations. Thus,there is a need for improved interference management for wirelessnetworks.

SUMMARY

A summary of sample aspects of the disclosure follows. It should beunderstood that any reference to the term aspects herein may refer toone or more aspects of the disclosure.

The disclosure relates in some aspect to managing interference throughthe use of fractional reuse techniques. For example, in some aspectsfractional reuse may involve using a portion of a set of allocatedhybrid automatic repeat-request (“HARQ”) interlaces for uplink trafficor downlink traffic. In some aspects fractional reuse may involve usinga portion of a timeslot allocated for uplink traffic or downlinktraffic. In some aspects fractional reuse may involve using a portion ofa frequency spectrum allocated for uplink traffic or downlink traffic.In some aspects fractional reuse may involve using a portion of a set ofspreading codes (e.g., SF16) allocated for uplink traffic or downlinktraffic. In some aspects, such portions may be defined and assigned suchthat neighboring nodes use non-overlapping resources. In some aspects,the definition and assignment of such portions may be based oninterference related feedback.

The disclosure relates in some aspects to managing interference throughthe use of power management-related techniques. For example, in someaspects transmit power of an access terminal may be controlled tomitigate interference at a non-associated access point. In some aspectsa noise figure or receive attenuation of an access point is controlledbased on the received signal strength associated with signals from oneor more access terminals.

The disclosure relates in some aspects to managing interference throughthe use of a transmit power profile and/or an attenuation profile. Forexample, downlink transmit power or uplink receiver continuation may bevaried dynamically at a node as a function of time. Here, differentnodes may use different phases of the profile to mitigate interferencebetween the nodes. In some aspects the profile may be defined based oninterference-related feedback.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other sample aspects of the disclosure will be described inthe detailed description and the appended claims that follow, and in theaccompanying drawings, wherein:

FIG. 1 is a simplified block diagram of several sample aspects of acommunication system;

FIG. 2 is a flowchart of several sample aspects of operations that maybe performed to manage interference;

FIG. 3 is a simplified block diagram illustrating several sample aspectsof components in a sample communication system;

FIG. 4 is a flowchart of several sample aspects of operations that maybe performed to manage interference through the use of HARQinterlace-based fractional reuse;

FIG. 5 is a flowchart of several sample aspects of operations that maybe performed to manage interference through the use of a transmit powerprofile;

FIG. 6 is a simplified diagram illustrating several aspects of a sampletransmit power profile;

FIG. 7 is a flowchart of several sample aspects of operations that maybe performed to manage interference through the use of a receiveattenuation profile;

FIG. 8 is a simplified diagram illustrating several aspects of a samplereceive attenuation profile;

FIGS. 9 and 10 are flowcharts of several sample aspects of operationsthat may be performed to manage interference through the use oftimeslot-based fractional reuse;

FIGS. 11 and 12 are flowcharts of several sample aspects of operationsthat may be performed to manage interference through the use offrequency spectrum-based fractional reuse;

FIGS. 13 and 14 are flowcharts of several sample aspects of operationsthat may be performed to manage interference through the use ofspreading code-based fractional reuse;

FIG. 15 is a flowchart of several sample aspects of operations that maybe performed to manage interference through the use of transmit powercontrol;

FIG. 16 is a simplified diagram illustrating several aspects of a samplepower control function;

FIG. 17 is a flowchart of several sample aspects of operations that maybe performed to manage interference by dynamically adjusting anattenuation factor;

FIG. 18 is a simplified diagram of a wireless communication system;

FIG. 19 is a simplified diagram of a wireless communication systemincluding femto nodes;

FIG. 20 is a simplified diagram illustrating coverage areas for wirelesscommunication;

FIG. 21 is a simplified block diagram of several sample aspects ofcommunication components; and

FIGS. 22-30 are simplified block diagrams of several sample aspects ofapparatuses configured to manage interference as taught herein.

In accordance with common practice the various features illustrated inthe drawings may not be drawn to scale. Accordingly, the dimensions ofthe various features may be arbitrarily expanded or reduced for clarity.In addition, some of the drawings may be simplified for clarity. Thus,the drawings may not depict all of the components of a given apparatus(e.g., device) or method. Finally, like reference numerals may be usedto denote like features throughout the specification and figures.

DETAILED DESCRIPTION

Various aspects of the disclosure are described below. It should beapparent that the teachings herein may be embodied in a wide variety offorms and that any specific structure, function, or both being disclosedherein is merely representative. Based on the teachings herein oneskilled in the art should appreciate that an aspect disclosed herein maybe implemented independently of any other aspects and that two or moreof these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein. Furthermore,an aspect may comprise at least one element of a claim.

FIG. 1 illustrates sample aspects of a communication system 100 wheredistributed nodes (e.g., access points 102, 104, and 106) providewireless connectivity for other nodes (e.g., access terminals 108, 110,and 112) that may be installed in or that may roam throughout anassociated geographical area. In some aspects, the access points 102,104, and 106 may communicate with one or more network nodes (e.g., acentralized network controller such as network node 114) to facilitatewide area network connectivity.

An access point such as access point 104 may be restricted whereby onlycertain access terminals (e.g., access terminal 110) are allowed toaccess the access point, or the access point may be restricted in someother manner. In such a case, a restricted access point and/or itsassociated access terminals (e.g., access terminal 110) may interferewith other nodes in the system 100 such as, for example, an unrestrictedaccess point (e.g., macro access point 102), its associated accessterminals (e.g., access terminal 108), another restricted access point(e.g., access point 106), or its associated access terminals (e.g.,access terminal 112). For example, the closest access point to givenaccess terminal may not be the serving access points for that accessterminal. Consequently, transmissions by that access terminal mayinterfere with reception at the access terminal. As discussed herein,fraction reuse, power control and other techniques may be employed tomitigate interference.

Sample operations of a system such as the system 100 will be discussedin more detail in conjunction with the flowchart of FIG. 2. Forconvenience, the operations of FIG. 2 (or any other operations discussedor taught herein) may be described as being performed by specificcomponents (e.g., components of the system 100 and/or components of asystem 300 as shown in FIG. 3). It should be appreciated, however, thatthese operations may be performed by other types of components and maybe performed using a different number of components. It also should beappreciated that one or more of the operations described herein may notbe employed in a given implementation.

For illustration purposes various aspects of the disclosure will bedescribed in the context of a network node, an access point, and anaccess terminal that communicate with one another. It should beappreciated, however, that the teachings herein may be applicable toother types of apparatuses or apparatuses that are referred to usingother terminology.

FIG. 3 illustrates several sample components that may be incorporatedinto the network node 114 (e.g., a radio network controller), the accesspoint 104, and the access terminal 110 in accordance with the teachingsherein. It should be appreciated that the components illustrated for agiven one of these nodes also may be incorporated into other nodes inthe system 100.

The network node 114, the access point 104, and the access terminal 110include transceivers 302, 304, and 306, respectively, for communicatingwith each other and with other nodes. The transceiver 302 includes atransmitter 308 for sending signals and a receiver 310 for receivingsignals. The transceiver 304 includes a transmitter 312 for transmittingsignals and a receiver 314 for receiving signals. The transceiver 306includes a transmitter 316 for transmitting signals and a receiver 318for receiving signals.

In a typical implementation, the access point 104 communicates with theaccess terminal 110 via one or more wireless communication links and theaccess point 104 communicates with the network node 114 via a backhaul.It should be appreciated that wireless or non-wireless links may beemployed between these nodes or other in various implementations. Hence,the transceivers 302, 304, and 306 may include wireless and/ornon-wireless communication components.

The network node 114, the access point 104, and the access terminal 110also include various other components that may be used in conjunctionwith interference management as taught herein. For example, the networknode 114, the access point 104, and the access terminal 110 may includeinterference controllers 320, 322, and 324, respectively, for mitigatinginterference and for providing other related functionality as taughtherein. The interference controller 320, 322, and 324 may include one ormore components for performing specific types of interferencemanagement. The network node 114, the access point 104, and the accessterminal 110 may include communication controllers 326, 328, and 330,respectively, for managing communications with other nodes and forproviding other related functionality as taught herein. The network node114, the access point 104, and the access terminal 110 may includetiming controllers 332, 334, and 336, respectively, for managingcommunications with other nodes and for providing other relatedfunctionality as taught herein. The other components illustrated in FIG.3 will be discussed in the disclosure that follows.

For illustrations purposes, the interference controller 320 and 322 aredepicted as including several controller components. In practice,however, a given implementation may not employ all of these components.Here, a HARQ controller component 338 or 340 may provide functionalityrelating to HARQ interlace operations as taught herein. A profilecontroller component 342 or 344 may provide functionality relating totransmit power profile or receive attenuation operations as taughtherein. A timeslot controller component 346 or 348 may providefunctionality relating to timeslot portion operations as taught herein.A spectral mask controller component 350 or 352 may providefunctionality relating to spectral mask operations as taught herein. Aspreading code controller component 354 or 356 may provide functionalityrelating to spreading code operations as taught herein. A transmit powercontroller component 358 or 360 may provide functionality relating totransmit power operations as taught herein. An attenuation factorcontroller component 362 or 364 may provide functionality relating toattenuation factor operations as taught herein.

FIG. 2 illustrates how the network node 114, the access point 104, andthe access terminal 110 may interact with one another to provideinterference management (e.g., interference mitigation). In someaspects, these operations may be employed on an uplink and/or on adownlink to mitigate interference. In general, one or more of thetechniques described by FIG. 2 may be employed in the more specificimplementations that are described in conjunction with FIGS. 4-18 below.Hence, for purposes of clarity, the descriptions of the more specificimplementations may not describe these techniques again in detail.

As represented by block 202, the network node 114 (e.g., theinterference controller 320) may optionally define one or moreinterference management parameters for the access point 104 and/or theaccess terminal 110. Such parameters may take various forms. Forexample, in some implementations the network node 114 may definefractional reuse parameters for mitigating interference on an uplinkand/or a downlink. As mentioned herein, such fractional reuse mayinvolve one or more of HARQ interlaces, puncturing, frequency spectrum,or spreading codes. In some implementations the network node 114 maydefine other types of interference management information such as, forexample, transmit power parameters, and receive attenuation parameters.Examples of such parameters will be described in more detail below inconjunction with FIGS. 4-18.

In some aspects, the definition of interference parameters may involvedetermining how to allocate one or more resources. For example, theoperations of block 402 may involve defining how an allocated resource(e.g., a frequency spectrum, etc.) may be divided up for fractionalreuse. In addition, the definition of fraction reuse parameters mayinvolve determining how much of the allocated resource (e.g., how manyHARQ interlaces, etc.) may be used by any one of a set of access points(e.g., restricted access points). The definition of fraction reuseparameters also may involve determining how much of the resource may beused by a set of access points (e.g., restricted access points).

In some aspects, the network node 114 may define a parameter based onreceived information that indicates whether there may be interference onan uplink or a downlink and, if so, the extent of such interference.Such information may be received from various nodes in the system (e.g.,access points and/or access terminals) and in various ways (e.g., over abackhaul, over-the-air, and so on).

For example, in some cases, one or more access points (e.g., the accesspoint 104) may monitor an uplink and/or a downlink and send anindication of interference detected on the uplink and/or downlink to thenetwork node 114 (e.g., on a repeated basis or upon request). As anexample of the former case, the access point 104 may calculate thestrength of signals it receives from nearby access terminals that arenot associated with (e.g., served by) the access point 104 (e.g., accessterminals 108 and 112) and report this to the network node 114.

In some cases, each of the access points in the system may generate aload indication when they are experiencing relatively high loading. Suchan indication may take the form of, for example, a busy bit in 1xEV-DO,a relative grant channel (“RGCH”) in 3GPP, or some other suitable form.In a conventional scenario, an access point may send this information toits associated access terminal via a downlink. However, such informationalso may be sent to the network node 114 (e.g., via the backhaul).

In some cases, one or more access terminals (e.g., the access terminal110) may monitor downlink signals and provide information based on thismonitoring. The access terminal 110 may send such information to theaccess point 104 (e.g., which may forward the information to the networknode 114) or to the network node 114 (via the access point 104). Otheraccess terminals in the system may send information to the network node114 in a similar manner.

In some cases, the access terminal 110 may generate measurement reports(e.g., on repeated basis). In some aspects, such a measurement reportmay indicate which access points the access terminal 110 is receivingsignals from, a received signal strength indication associated with thesignals from each access point (e.g., Ec/Io), the path loss to each ofthe access points, or some other suitable type of information. In somecases a measurement report may include information relating to any loadindications the access terminal 110 received via a downlink.

The network node 114 may then use the information from one or moremeasurement reports to determine whether the access point 104 and/or theaccess terminal 110 are relatively close to another node (e.g., anotheraccess point or access terminal). In addition, the network node 114 mayuse this information to determine whether any of these nodes interferewith any other one of these nodes. For example, the network node 114 maydetermine received signal strength at a node based on the transmit powerof a node that transmitted the signals and the path loss between thesenodes.

In some cases, the access terminal 110 may generate information that isindicative of the signal to noise ratio (e.g., signal and interferenceto noise ratio, SINR) on a downlink. Such information may comprise, forexample a channel quality indication (“CQI”), a data rate control(“DRC”) indication, or some other suitable information. In some cases,this information may be sent to the access point 104 and the accesspoint 104 may forward this information to the network node 114 for usein interference management operations. In some aspects, the network node114 may use such information to determine whether there is interferenceon a downlink or to determine whether interference in the downlink isincreasing or decreasing.

As will be described in more detail below, in some cases theinterference-related information may be used to determine how to deployfractional reuse to mitigate interference. As one example, CQI or othersuitable information may be received on a per-HARQ interlace basiswhereby it may be determined which HARQ interlaces are associated withthe lowest level of interference. A similar technique may be employedfor other fractional reuse techniques.

It should be appreciated that the network node 114 may define parametersin various other ways. For example, in some cases the network node 114may randomly select one or more parameters.

As represented by block 204, the network node 114 (e.g., thecommunication controller 326) sends the defined interference managementparameters to the access point 104. As will be discussed below, in somecases the access point 104 uses these parameters and in some cases theaccess point 104 forwards these parameters to the access terminal 110.

In some cases, the network node 114 may manage interference in thesystem by defining the interference management parameters to be used bytwo or more nodes (e.g., access points and/or access terminals) in thesystem. For example, in the case of a fractional reuse scheme, thenetwork node 114 may send different (e.g., mutually exclusive)interference management parameters to neighboring access points (e.g.,access points that are close enough to potentially interfere with oneanother). As a specific example, the network node 114 may assign a firstHARQ interlace to the access point 104 and assign a second HARQinterlace to the access point 106. In this way, communication at onerestricted access point may not substantially interfere withcommunication at the other restricted access point. Similar techniquesmay be employed for other fractional reuse schemes and for accessterminals in the system.

As represented by block 206, the access point 104 (e.g., theinterference controller 322) determines interference managementparameters that it may use or that it may send to the access terminal110. In cases where the network node 114 defines the interferencemanagement parameters for the access point 104, this determinationoperation may simply involve receiving the specified parameters and/orretrieving the specified parameters (e.g., from a data memory).

In some cases the access point 104 determines the interferencemanagement parameters on its own. These parameters may be similar to theparameters discussed above in conjunction with block 202. In addition,in some cases these parameters may be determined in a similar manner asdiscussed above at block 202. For example, the access point 104 mayreceive information (e.g., measurement reports, CQI, DRC) from theaccess terminal 110. In addition, the access point 104 may monitor anuplink and/or a downlink to determine the interference on such a link.The access point 104 also may randomly select a parameter.

In some cases, the access point 104 may cooperate with one or more otheraccess points to determine an interference management parameter. Forexample, in some cases the access point 104 may communicate with theaccess point 106 to determine which parameters are being used by theaccess point 106 (and thereby selects different parameters) or tonegotiate the use of different (e.g., mutually exclusive) parameters. Insome cases, the access point 104 may determine whether it may interferewith another node (e.g., based on CQI feedback that indicates thatanother node is using a resource) and, if so, define its interferencemanagement parameters to mitigate such potential interference.

As represented by block 208, the access point 104 (e.g., thecommunication controller 328) may send interference managementparameters or other related information to the access terminal 110. Forexample, in some cases this information may indicate how fractionalreuse is deployed (e.g., which HARQ interlaces are to be used, whichspectral mask is to be used, etc.) on an uplink or downlink between theaccess point 104 and the access terminal 110. In some cases thisinformation may relate to power control (e.g., specifies uplink transmitpower).

As represented by blocks 210 and 212, the access point 104 may thustransmit to the access terminal 110 on the downlink or the accessterminal 110 may transmit to the access point 104 on the uplink. Here,the access point 104 may use its interference management parameters totransmit on the downlink and/or receive on the uplink. Similarly, theaccess terminal 110 may take these interference management parametersinto account when receiving on the downlink or transmitting on theuplink.

In some implementations, the access terminal 110 (e.g., the interferencecontroller 324) may define one or more interference managementparameters. Such a parameter may be used by the access terminal 110and/or sent (e.g., by the communication controller 330) to the accesspoint 104 (e.g., for use during uplink operations).

Referring now to FIG. 4, operations relating to the use of a fractionalreuse scheme employing HARQ interlaces on an uplink or a downlink willbe described in more detail. In some aspects the system 100 may employtime division multiplexing whereby information may be transmitting onone or more defined timeslots. Such timeslots may take various formsand/or be referred to using various terminology. As an example, invarious implementations a timeslot may relate to or be referred to as aframe, a subframe, a slot, a transmission time interval (“TTI”), an HARQinterlace, and so on. As an example, a predetermined number of timeslots(e.g., TTIs) 1 through 16 may be monitored and used for downlinktransmission. A similar scheme may be used for uplink transmission.

Based on traffic and associated interference levels on the monitoredslots, and based on application of one or more of the schemes taughtherein, uplink or downlink transmission may be limited to a definednumber of slots N, where N=8, for example, lower than the total numberof slots M, where M=16, for example. In some aspects such a fractionalreuse scheme may utilize HARQ interlaces.

In a conventional 1xEV-DO system, each HARQ process may be assigned, forexample, every fourth subframe, such that HARQ retransmissions of anoriginal transmission in subframe “n” are performed in slots (n+4),(n+8), (n+12), etc. As a specific example, HARQ interlace 1 may beassigned subframes 1, 5, 9, and so on. In the event an original datatransmission for HARQ interlace 1 during subframe 1 is unsuccessful, anegative acknowledgement (“NACK”) signal may be sent on a complementarylink (e.g., an uplink in the case of a downlink HARQ transmission). Thedata may then be retransmitted during subframe 5 of the same HARQinterlace 1 and, upon a successful transmission, an acknowledgement(“ACK”) signal is received (e.g., via an uplink). Similar operations maybe performed by other HARQ processes on the other HARQ interlaces 2, 3,and 4.

In some aspects, a fractional reuse scheme may utilize HARQ interlacesto configure neighboring nodes (e.g., access points and/or accessterminals) to transmit at different times. For example, a first accesspoint may transmit during HARQ interlaces 1 and 2 while a second accesspoint transmits during HARQ interlaces 3 and 4. As a result,interference that may otherwise occur between the nodes may be reduced.

As represented by block 402 of FIG. 4, the network node 114 (e.g., anHARQ control component 338 of the interference controller 320)determines how many HARQ interlaces may be used by each access point(e.g., in a set of restricted access points). For example, a definednumber “N” of HARQ interlaces lower than the total number “M” of HARQinterlaces allocated for the set may be determined based oninterference-related feedback from one or more access points and/oraccess terminals in the system (e.g. as discussed above in conjunctionwith FIG. 2). Thus, at any given time, the number N of downlink (oruplink) HARQ interlaces out of the total number M of HARQ interlaces maybe defined based on the downlink (or uplink) activity of neighboringnodes on the M HARQ interlaces.

N may be a fixed value or dynamically defined. In a case where M=4, Nmay be dynamically set between a minimum value N_(MIN) greater than zeroand a maximum value N_(MAX) lower than 4. In some cases the value N maybe randomly determined. Typically, however, the value N may be selectedin an effort to more effectively mitigate interference between nodes inthe system. The determination of the value N may be based on variouscriteria.

For example, one criterion may relate to how access points are deployedin the system (e.g., the total number of access points, the density ofaccess points within a given area, the relative proximity of the accesspoints, and so on). Here, if there are a large number of nodes that areclose to one another, a smaller value of N may be used so thatneighboring nodes may be less likely to use the same HARQ interlaces.Conversely, if there are a small number of nodes in the system, a largervalue of N may be defined to improve communication performance (e.g.,throughput).

Another criterion may relate to the traffic (e.g., the amount oftraffic, the types of traffic, the quality of service requirements ofthe traffic) handled by the access points. For example, some types oftraffic may be more sensitive to interference than other types oftraffic. In such a case, a smaller value of N may be used. In addition,some types of traffic may have stricter throughput requirements (butless sensitivity to interference) whereby a larger value for N may beused.

In some cases, the network node 114 may define the value N based onreceived interference-related information (e.g., as discussed at FIG.2). For example, the number of access points heard by a given accessterminal and the relative proximity of the access points to the accessterminal may be determined based on measurement reports received fromthe access terminal. In this way, the network node 114 may determinewhether transmissions at a given cell (e.g., by a restricted accesspoint or its associated access terminals) may interfere with aneighboring cell and define N accordingly.

The network node 114 also may define N based on interference informationreceived from one or more access points (e.g., as discussed at FIG. 2).For example, if interference values are high, a lower value of N may bedefined. In this way, the number of HARQ interlaces used by a givenaccess point may be reduced thereby reducing the probability ofinterference on each set of N HARQ interlaces out of the total number ofHARQ interlaces M.

As represented by block 404, in some cases the network node 114 mayspecify specific HARQ interlaces to be used by specific access points.For example, the network node 114 may determine the amount ofinterference that may be seen on each of the M HARQ interlaces by agiven access point and assign HARQ interlaces having lower interferenceto that access point. As a specific example, the network node 114 maydetermine that downlink transmission by the access point 106 on the twoHARQ interlaces (e.g., interlaces 3 and 4) that it is using mayinterfere with reception at the access terminals associated with theaccess point 104. This may be determined, for example, based on thedownlink interference-related information that the network node mayacquire as discussed herein. The network node 114 may then designateHARQ interlaces 1 and 2 for use by the access point 104.

As mentioned above, the determination of interference on each HARQinterlace may be based on signals received by the network node 114. Forexample, the likelihood of interference between nodes may be determinedbased on one or more measurement reports received from one or moreaccess terminals as discussed herein. In addition, for the downlink,access terminals in the system may generate channel quality indication(“CQI”) or data rate control (“DRC”) information for each HARQ interlace(e.g., for each TTI in 3GPP) and forward this information to the networknode 114. Also for the downlink, an access terminal may monitor thedownlink and provide interference-related information on a per-HARQinterlace (e.g., per-TTI) basis. Similarly, for the uplink an accessterminal may monitor the uplink and provide interference-relatedinformation on a per-HARQ interlace (e.g., per-TTI) basis. In some cases(e.g., DRC feedback in 3GPP2), the feedback from an access terminal maynot provide per-HARQ interlace resolution. In such a case, ACK/NACKfeedback or some other type of feedback may be employed to identify adesired set of HARQ interlaces. As another example, downlink data ratemay be adjusted on a given HARQ interlace to determine the rate at whichthe access terminal can successfully decode the data (e.g., with a givenaccuracy). Based on the best data rate determined for each HARQinterlace, an assumption may be made as to which HARQ interlace willprovide the best performance for a given access point. Alternatively, acentralized HARQ interlace selection scheme may be employed (e.g., wherethe network node designates the HARQ interlaces for neighboring nodes asdiscussed herein).

In some aspects, the designation of specific HARQ interlaces by thenetwork node 114 may be dependent on whether the corresponding uplink ordownlink traffic is synchronized. Such synchronization may be achieved,for example, using an adjustment such as Tau-DPCH (where DPCH relates toa dedicated physical channel) or some other suitable synchronizationscheme.

In some aspects, the network node 114 may designate consecutive HARQinterlaces for a given access point. In this way, in the event theuplink or downlink traffic of different nodes is not synchronized, atleast a portion of the designated HARQ interlaces may not be subject tointerference. As an example, if HARQ interlaces 1-4 are assigned to afirst access point and HARQ interlaces 5-8 are assigned to a secondaccess point, these access points will not be subjected to interferencefrom the other access point on at least three of the HARQ interlaceseven if the timing of the access points is not synchronized.

As represented by block 406, the network node 114 then sends the HARQinterlace parameters it defined to one or more access points. Forexample, a network node 114 may send a node-specific designation to eachaccess point or the network node 114 may send a common designation toall of the access points in a set of access points.

As represented by block 408, the access point 104 (e.g., a HARQ controlcomponent 340 of the interference controller 322) determines the HARQinterlaces it will use for uplink or downlink communication. Here, theaccess point 104 will have received the value N from the network node114. In the event the network node 114 designated the HARQ interlaces tobe used by the access point 104 the access point 104 may simply usethese HARQ interlaces. In some cases, the access point 104 may randomlyselect a parameter.

If the HARQ interlaces were not designated by the network node 114 orselected randomly, the access point 104 may determine which N HARQinterlaces to use based on appropriate criteria. Initially, thisdetermination is thus based on (e.g., constrained by) the value N. Insome cases the access point 104 may define or adapt N (e.g., based oncriteria as discussed above).

In some cases the access point 104 may select the HARQ interlacesassociated with the lowest interference. Here, the access point 104 maydetermine which HARQ interlaces to use in a similar manner as discussedabove. For example, the access point 104 may receive information (e.g.,measurement reports, CQI, DRC) from the access terminal 110. Inaddition, the access point 104 may monitor an uplink and/or a downlinkto determine the interference on such a link. For example, when theaccess point 104 is idle, it may monitor uplink interference (load) fromout-of-cell. In this way, the access point 104 may select the HARQinterlaces that provide minimal out-of-cell interference.

In some cases, the access point 104 may cooperate with one or more otheraccess points to determine the HARQ interlaces it will use. For example,the access point 104 and the access point 106 may negotiate to usedifferent (e.g., mutually exclusive) HARQ interlaces.

As represented by block 410, the access point 104 may determine a timingoffset to use for uplink or downlink communication. For example, theaccess point 104 may continuously monitor a link over a period of timeto determine approximately when a neighboring node commences and endsits transmissions. In this way, the access point 104 may determine(e.g., estimate) the timeslot timing of the neighboring node. The accesspoint may then synchronize the timeslot timing of its uplink or downlinkto that time. In some aspects this may be involve defining a Tau-DPCHparameter.

In some cases (e.g., 3GPP), access points may synchronize their timing(e.g., HS-PDSCH timing) by time aligning their P-CCPCHs (primary-commoncontrol physical channel). Such synchronization may be achieved, forexample, through the use of GPS components in each access point, timingsignaling between access points (which may be relatively effective forneighboring access points, e.g., with tens of meters of one another), orsome other technique.

In some cases (e.g., in HSDPA), overhead may be relatively high and notorthogonal to traffic. Here, discontinuous transmission or reception(DTX or DRX) may be employed whereby overhead is not transmitted duringthe DTX/DRX period. In such cases, transmission for CCPCH and EHICH maybe accounted for and access terminals may be configured to account forthe lower CPICH Ec/Io measurements they may see from access pointsemploying DTX/DRX.

As represented by block 412, the access point 104 may send a message toan associated access terminal to inform the access terminal which HARQinterlaces are to be used for the uplink or downlink. In someimplementations, the access point 104 may use E-AGCH (enhanced-absolutegrant channel) or some other similar mechanism to send the HARQinterlaces designations to its associated access terminals. For example,the access point 104 may set Xags=1 to specify which TTIs the accessterminal is to use. In addition, the access point 104 may send anindication of the timing offset (e.g., Tau-DPCH) determined at block 410to the access terminal. In this way, the access point may schedule datatransmissions (uplink or downlink) on the best N HARQ interlaces out ofthe available M HARQ interlaces (block 414).

The HARQ interlace parameters (e.g., N and the specific HARQ interlacesused by a given node) described above may be adjusted over time. Forexample, the information described above may be collected on a repeatedbasis and the parameters adjusted accordingly (e.g., with hysteresisand/or slow filtering if desired). In this way, the HARQ interlaces maybe deployed in a manner that accounts for current interferenceconditions in the system.

In some implementations HARQ interlaces may be allocated in ahierarchical manner. For example, if no restricted access points aredeployed in a coverage area of a macro access point, a full set of HARQinterlaces (e.g., 8) may be allocated for a macro access point. In theevent restricted access points are deployed in the coverage area of themacro access point, however, one portion of the HARQ interlaces (e.g.,5) may be allocated for macro coverage and another portion of the HARQinterlaces (e.g., 3) may be allocated for the restricted access points.The HARQ interlaces allocated for the restricted access points may thenbe allocated among the restricted access points (e.g., N=1) as describedabove. The number of HARQ interlaces allocated in this way may bedefined (e.g., in a fixed manner or dynamically adjusted) based onvarious criteria as discussed herein (e.g., restricted access pointdeployment, traffic, interference, etc.). For example, as the number ofrestricted access points in the system or the amount of traffic at therestricted access points increases the number of HARQ interlacesallocated for these access points may be increased.

Referring now to FIGS. 5 and 6, operations relating to the use of ascheme for varying transmit power (e.g., downlink transmit power) overtime to mitigate interference will be described in more detail. In someaspects this scheme involves defining a transmit power profile such asthe profile 602 shown in FIG. 6 that defines different power levels overtime. Such a profile may take various forms and be defined in variousways. For example, in some cases a profile may comprise a set of valuesthat define the transmit power for different points in time. In somecases a profile may be defined by an equation (e.g., a sinusoidalwaveform). In some aspects a profile may be periodic. As shown in FIG.6, a maximum value (MAX), a minimum value (MIN) and a period 604 may bedefined for the profile.

A transmit power profile may be used to control transmit power indifferent ways. For example, in some cases the transmit power profile isused to control total transmit power. In some implementations, overheadchannels (e.g., CPICH, etc.) and dedicated channels may operate at aconstant power. Leftover power according to the transmit power profilemay then be shared among the other channels (e.g., HS-SCCH andHS-PDSCH). In some implementations overhead channels may be scaled.

As described in more detail below, in some aspects transmit power-basedfractional reuse may be achieved through the use of a transmit powerprofile. For example, neighboring access points may use the same profile(or a similar profile) but do so based on different phases of theprofile. For example, a first access point may transmit according to theprofile shown in FIG. 6 while a second access point transmits using thesame profile shifted by 180 degrees. Thus, when the first access pointis transmitting at maximum power the second access point may betransmitting at minimum power.

As represented by block 502 of FIG. 5, the network node 114 (e.g., aprofile control component 342 of the interference controller 320)defines (e.g., specifies) transmit power profile information to be usedfor wireless transmission (e.g., over a downlink). This information mayinclude, for example, parameters such as the transmit power profile,initial minimum and maximum values, and an initial period value.

In some cases one or more of these parameters may be predefined orrandomly determined. Typically, however, these parameters are selectedin an effort to more effectively mitigate interference between nodes inthe system. The determination of this information may be based onvarious criteria such as, for example, one or more measurement reportsfrom one or more access terminals, one or more reports from one or moreaccess points regarding the CQI reported by one or more associatedaccess terminals, the number of active access terminals, and the averagedownlink traffic at each access point (e.g., in each cell).

As a specific example, the definition of a transmit power profileparameter may be based on how access points are deployed in the system(e.g., the total number of access points, the density of access pointswithin a given area, the relative proximity of the access points, and soon). Here, if there are a large number of nodes that are close to oneanother the parameters may be defined so that neighboring nodes may beless likely to transmit at a high power at the same time. As an example,the transmit power profile may be shaped such that a given access pointmay transmit at or near maximum power for a relatively short period oftime. In this way, the transmit power profile may provide adequateisolation when a large number of phase values (e.g., 60 degrees, 120degrees, etc.) are used by various nodes in the system in conjunctionwith the transmit power profile. Conversely, if there are a small numberof nodes in the system the parameters may be defined to improvecommunication performance (e.g., throughput). As an example, thetransmit power profile may be shaped such that a given access point maytransmit at or near maximum power for a longer period of time.

Different levels of isolation between neighboring access points (e.g.,cells) also may be achieved by adjusting the magnitudes of the minimumand maximum parameters. For example, a larger max/min ratio providesbetter isolation at the expense of having longer periods of time wherean access terminal is transmitting at a lower power level.

A transmit power profile parameter may be defined based on the traffic(e.g., the traffic load, the types of traffic, the quality of servicerequirements of the traffic) handled by the access points. For example,some types of traffic may be more sensitive to interference than othertypes of traffic. In such a case, a parameter (e.g., the transmit powerprofile or max/min) that provides higher isolation may be used (e.g., adiscussed above). In addition, some types of traffic may have stricterthroughput requirements (but less sensitivity to interference) whereby atransmit power profile that allows more transmissions at higher powerlevels may be used (e.g., a discussed above).

In some cases, the network node 114 may define the transmit powerprofile parameters based on received interference-related information(e.g., feedback from one or more access points and/or access terminalsin the system as discussed above in conjunction with FIG. 2). Forexample, the number of access points heard by a given access terminaland the relative proximity of the access points to the access terminalmay be determined based on measurement reports received from the accessterminal. In this way, the network node 114 may determine whethertransmissions at a given cell (e.g., associated with a restricted accesspoint) may interfere with a neighboring cell and adjust the powerprofile parameters accordingly. The network node 114 also may define theparameters based on interference information received from one or moreaccess points (e.g., as discussed at FIG. 2).

In some implementations the period parameter may be defined based on atradeoff between any delay sensitivity of application data (e.g., VoIP)and CQI/DRC filtering/delay (e.g., the delay from the time SINR ismeasured to the time it is effective at a traffic scheduler for theaccess point). For example, if cells are carrying a large amount of VoIPtraffic, the period may be set to correspond to the periodicity of VoIPpackets. In some cases, a period in the range of 50-100 ms may beappropriate. In some implementations the period parameter may be definedbased on the number of access terminals being serviced.

As represented by block 504, in some cases the network node 114 mayspecify specific phase offset values to be used by specific accesspoints. For example, the network node 114 may determine the amount ofinterference that may be seen by a given access point when it usesdifferent values of the phase offset (e.g., based on CQI reportsreceived for each TTI). The phase offset associated with the lowestinterference at that access point may then be assigned to that accesspoint.

The network node 114 also may designate phase offset values forneighboring nodes in a manner that mitigates interference between thenodes. As a specific example, the network node 114 may determine thatdownlink transmission by the access point 106 may interfere withreception at an access terminal associated with the access point 104.This may be determined, for example, based on the downlinkinterference-related information that the network node 114 may acquireas discussed herein. The network node 114 may then designate differentphase offset values (e.g., 180 degrees out of phase) for the accesspoints 104 and 106.

As represented by block 506, the network node 114 then sends the powerprofile information it defined to one or more access points. Here, thenetwork node 114 may send a node-specific designation to each accesspoint or the network node 114 may send a common designation to all ofthe access points in a set of access points.

As represented by blocks 508 and 510, the access point 104 (e.g., aprofile control component 344 of the interference controller 322)determines the transmit power profile parameters it will use fordownlink communication. In the event the network node 114 designated allof the transmit power profile parameters to be used by the access point104, the access point 104 may simply use these parameters. In somecases, the access point 104 may randomly select a parameter (e.g., thephase offset).

If all of the parameters were not designated by the network node 114 orselected randomly, the access point 104 may determine which parametersto use based on appropriate criteria. In a typical case, the accesspoint may implement a tracking algorithm to dynamically determine aphase offset value to use in conjunction with the transmit powerprofile, minimum, maximum, and period parameters the access point 104received from the network node 114.

In some cases the access point 104 may select the phase offset valuethat is associated with the lowest interference. Here, the access point104 may determine which phase offset value to use in a similar manner asdiscussed above. For example, at block 508 the access point 104 mayreceive information (e.g., measurement reports, CQI, DRC) from theaccess terminal 110 and/or the access point 104 may monitor a link todetermine the interference on the link. As an example of the lattercase, when the access point 104 is idle, it may monitor interference(load) from out-of-cell on the downlink. In this way, the access point104 may select the phase offset value that provides minimal out-of-cellinterference at block 510.

In some cases, the access point 104 may cooperate with one or more otheraccess points to determine the phase offset value. For example, theaccess point 104 and the access point 106 may negotiate to use different(e.g., out of phase) phase offset values. In such a case, the operationsof block 508 may not be performed.

As represented by block 512, the access point transmits on the downlinkbased on the current transmit power profile. Thus, the transmit powermay vary over time in a manner that may mitigate interference withneighboring nodes.

The transmit power profile parameters (e.g., maximum, minimum, andperiod parameters defined by the network node 114) described above maybe adjusted over time. For example, the information described above maybe collected on a repeated basis and the parameters adjusted accordingly(e.g., with hysteresis and/or slow filtering if desired). In this way,transmit power of the access terminals in the system may be controlledin a manner that accounts for current interference conditions in thesystem. For example, if interference increases at a given node (e.g., asdetermined by CQI reports), the maximum power parameter may be reduced.In a simplified case, maximum_i is set equal to minimum_i for eachaccess point_i. The network node 114 may then attempt to set thesevalues to provide the same (or substantially the same) average CQI ineach cell which may be achieved using the Ec_i,j/Io measurement of eachaccess terminal_j from each access point_i.

Referring now to FIGS. 7 and 8, operations relating to the use of ascheme for varying receive attenuation (e.g., uplink attenuation) overtime to mitigate interference will be described in more detail. In someaspects this scheme involves defining a receive attenuation profile suchas the profile 802 shown in FIG. 8 that defines different attenuationlevels over time. Such a profile may take various forms and be definedin various ways. For example, in some cases a profile may comprise a setof values that define the receive attenuation for different points intime. In some cases a profile may be defined by an equation (e.g., asinusoidal waveform). As shown in FIG. 8, a maximum value (MAX), aminimum value (MIN) and a period 804 may be defined for the profile.

As described in more detail below, in some aspects receiveattenuation-based fractional reuse may be achieved through the use of areceive attenuation profile. For example, neighboring access points mayuse the same profile (or a similar profile) but do so based on differentphases of the profile. For example, a first access point may receiveaccording to the profile shown in FIG. 8 while a second access pointreceives using the same profile shifted by 180 degrees. Thus, when thefirst access point is receiving at maximum attenuation the second accesspoint may be receiving at minimum attenuation.

As represented by block 702 of FIG. 7, the network node 114 (e.g., aprofile component 342 of the interference controller 320) definesreceive attenuation profile information to be used for wirelessreception (e.g., over an uplink). This information may include, forexample, parameters such as the receive attenuation profile, initialminimum and maximum values, and an initial period value.

In some cases one or more of these parameters may be predefined orrandomly determined. Typically, however, these parameters are selectedin an effort to more effectively mitigate interference between nodes inthe system. The determination of this information may be based onvarious criteria such as, for example, one or more measurement reportsfrom one or more access terminals, one or more reports from one or moreaccess points regarding the CQI reported by one or more associatedaccess terminals, the number of active access terminals, and the averageuplink traffic at each access point (e.g., in each cell).

As a specific example, the definition of a receive attenuation profileparameter may be based on how access points are deployed in the system(e.g., the total number of access points, the density of access pointswithin a given area, the relative proximity of the access points, and soon). Here, if there are a large number of nodes that are close to oneanother the parameters may be defined so that neighboring nodes may beless likely to receive at a high attenuation level at the same time. Asan example, the receive attenuation profile may be shaped such that agiven access point may receive at or near maximum attenuation for arelatively short period of time. In this way, the receive attenuationprofile may provide adequate isolation when a large number of phasevalues (e.g., 60 degrees, 120 degrees, etc.) are used by various nodesin the system in conjunction with the receive attenuation profile.Conversely, if there are a small number of nodes in the system theparameters may be defined to improve communication performance (e.g.,throughput). As an example, the receive attenuation profile may beshaped such that a given access point may receive at or near a maximumattenuation level for a longer period of time.

Different levels of isolation between neighboring access points (e.g.,cells) also may be achieved by adjusting the magnitudes of the minimumand maximum parameters. For example, a larger max/min ratio providesbetter isolation at the expense of having longer periods of time wherean access terminal is receiving at a lower attenuation level.

A receive attenuation profile parameter may be defined based on thetraffic (e.g., the traffic load, the types of traffic, the quality ofservice requirements of the traffic) handled by the access points. Forexample, some types of traffic may be more sensitive to interferencethan other types of traffic. In such a case, a parameter (e.g., thereceive attenuation profile or max/min) that provides higher isolationmay be used (e.g., a discussed above). In addition, some types oftraffic may have stricter throughput requirements (but less sensitivityto interference) whereby a receive attenuation profile that allows moretransmissions at higher attenuation levels may be used (e.g., adiscussed above).

In some cases the network node 114 may define the receive attenuationprofile parameters based on received interference-related information(e.g., feedback from one or more access points and/or access terminalsin the system as discussed above in conjunction with FIG. 2). Forexample, the number of access points heard by given access terminal andthe relative proximity of the access points to the access terminal maybe determined based on measurement reports received from the accessterminal. In this way, the network node 114 may determine whethertransmissions at a given cell (e.g., associated with a restricted accesspoint) may interfere with a neighboring cell and adjust the attenuationprofile parameters accordingly. The network node 114 also may define theparameters based on interference information received from one or moreaccess points (e.g., as discussed at FIG. 2).

In some implementations the period parameter may be defined based on atradeoff between any delay sensitivity of application data (e.g., VoIP)and downlink control channel (e.g., CQI/DRC, ACK channel, etc.)filtering/delay as discussed above.

As represented by block 704, in some cases the network node 114 mayspecify specific phase offset values and/or other parameters discussedabove to be used by specific access points. For example, the networknode 114 may determine the amount of interference that may be seen by agiven access point when it uses different values of the phase offset.The phase offset associated with the lowest interference at that accesspoint may then be assigned to that access point.

The network node 114 also may designate phase offset values forneighboring nodes in a manner that mitigates interference between thenodes. As a specific example, the network node 114 may determine thatuplink transmission by the access terminal 112 may interfere withreception at the access point 104. This may be determined, for example,based on the uplink interference-related information that the networknode 114 may acquire as discussed herein. The network node 114 may thendesignate different (e.g., 180 degrees out of phase) phase offset valuesfor the access points 104 and 106.

As represented by block 706, the network node 114 then sends theattenuation profile information it defined to one or more access points.Here, the network node 114 may send a node-specific designation to eachaccess point or the network node 114 may send a common designation toall of the access points in a set of access points.

As represented by blocks 708 and 710, the access point 104 (e.g., aprofile component 344 of the interference controller 322) determines thereceive attenuation profile parameters it will use for uplinkcommunication. In the event the network node 114 designated all of thereceive attenuation profile parameters to be used by the access point104, the access point 104 may simply use these parameters. In somecases, the access point 104 may randomly select a parameter (e.g., thephase offset).

If all of the parameters were not designated by the network node 114 orselected randomly, the access point 104 may determine which parametersto use based on appropriate criteria. In a typical case, the accesspoint may implement a tracking algorithm to dynamically determine aphase offset value to use in conjunction with the receive attenuationprofile, minimum, maximum, and period parameters the access point 104received from the network node 114.

In some cases the access point 104 may select the phase offset valuethat is associated with the lowest interference. Here, the access point104 may determine which phase offset value to use in a similar manner asdiscussed above. For example, at block 708 the access point 104 mayreceive information (e.g., measurement reports) from the access terminal110 and/or the access point 104 may monitor a link to determine theinterference on the link. As an example of the latter case, when theaccess point 104 is idle, it may monitor interference (load) fromout-of-cell on the uplink. In this way, the access point 104 may selectthe phase offset value that provides minimal out-of-cell interference atblock 710.

In some cases, the access point 104 may cooperate with one or more otheraccess points to determine the phase offset value. For example, theaccess point 104 and the access point 106 may negotiate to use different(e.g., out of phase) phase offset values. In such a case, the operationsof block 708 may not be performed.

As represented by block 712, the access point receives on the uplinkbased on the current receive attenuation profile (e.g., by applying theattenuation profile to received signals). Thus, the receive attenuationmay vary over time in a manner that may mitigate interference withneighboring nodes.

The receive attenuation profile parameters (e.g., maximum, minimum, andperiod parameters defined by the network node 114) described above maybe adjusted over time. For example, the information described above maybe collected on a repeated basis and the parameters adjusted accordingly(e.g., with hysteresis and/or slow filtering if desired). In this way,receive attenuation of the access terminals in the system may becontrolled in a manner that accounts for current interference conditionsin the system. For example, the attenuation (e.g., maximum attenuation)may be increased as the received signal power level at one or moreaccess points increases. In a simplified case, maximum_i is set equal tominimum_i for each access point_i and controlled in a similar manner asdiscussed above.

Referring now to FIGS. 9 and 10, operations relating to the use of afractional reuse scheme employing selective transmission (e.g.,puncturing) on an uplink or a downlink will be described in more detail.As mentioned above, a system may transmit during one or more definedtimeslots which, in various implementations, may relate to or bereferred to as a frame, a subframe, a slot, a transmission time interval(“TTI”), an HARQ interlace, and so on.

In some aspects, a fractional reuse scheme may involve configuringneighboring nodes (e.g., access points and/or access terminals) torefrain from transmitting during a portion of one or more transmittimeslots. For example, a first access point may transmit during a firstportion (e.g., a part or the entirety of a subframe) of a timeslot whilea second access point transmits during a second portion (e.g., anotherpart of the subframe or the entirely of a different subframe) of atimeslot. As a result, interference that may otherwise occur between thenodes may be reduced.

In some aspects, a determination as to whether a node will refrain fromtransmitting during a given portion of a timeslot may involvedetermining how much interference is present on different portions ofthe timeslot. For example, a node may refrain from transmitting on thoseportions of a time slot that are associated with higher interference.

Referring initially to FIG. 9, as represented by block 902, the networknode 114 (e.g., a timeslot control component 346 of the interferencecontroller 320) or some other suitable entity may determine how a giventransmit timeslot or a set of transmit timeslots is/are to be dividedinto portions so that different nodes may selectively refrain fromtransmitting during one or more of these timeslot portions. This mayinvolve, for example, determining parameters such as the structure ofeach timeslot portion, the number of timeslot portions, the size of eachtimeslot portion, and the location of each timeslot portion. Here, itshould be appreciated that a given timeslot portion may be defined toinclude subportions that are not contiguous in time or may be defined asa single contiguous period of time. In some cases, these timeslotparameters may be predefined for a system.

In some aspects the parameters of the timeslot portions are defined tomitigate interference in a system. To this end, the timeslot portionsmay be defined based on how nodes are deployed in the system (e.g., thetotal number of access points, the density of access points within agiven area, the relative proximity of the access points, and so on).Here, if there are a large number of nodes deployed in a given area,more timeslot portions (e.g., and possibly smaller portions) may bedefined and/or more separation may be provided between the timeslotportions. In this way, neighboring nodes may be less likely to use thesame timeslot portion (or interference with a neighboring timeslotportion) and any potentially interfering nodes may thereby be configuredto not transmit during a larger percentage of a timeslot or set oftimeslots. Conversely, if there are a smaller number of nodes in thesystem fewer timeslot portions (e.g., and possibly larger portions withless separation) may be defined to improve communication performance(e.g., throughput).

The timeslot portions also may be defined based on the traffic (e.g.,the amount of traffic, the types of traffic, the quality of servicerequirements of the traffic) handled by the access points. For example,some types of traffic may be more sensitive to interference than othertypes of traffic. In such a case, more timeslot portions may be definedand/or more separation may be provided between the timeslot portions. Inaddition, some types of traffic may have stricter throughputrequirements (but less sensitivity to interference) whereby largertimeslot portions may be defined.

The timeslot portions also may be defined based on interference in thesystem. For example, if interference values are high in the system, moretimeslot portions may be defined and/or more separation may be providedbetween the timeslot portions.

The operations of block 902 may therefore be based oninterference-related feedback from one or more access points and/oraccess terminals in the system (e.g. as discussed above). For example,access terminal measurement reports and/or reports from access nodes maybe used to determine the extent to which the nodes in the system mayinterfere with one another.

As represented by block 904, in some cases the network node 114 mayspecify specific timeslot portions to be used by specific nodes. In somecases the timeslot portions may be assigned in a random manner.Typically, however, the timeslot portions may be selected in an effortto mitigate interference between nodes in the system. In some aspects, adetermination of which timeslot portion a given node should use may besimilar to the operations of block 902 described above. For example, thenetwork node 114 may determine the amount of interference that isassociated with the timeslot portions.

For a downlink, an access point may first be configured to use a firsttimeslot portion. Interference associated with the use of that timeslotportion may then be determined (e.g., based on CQI reports collectedover a period of time). The access point may then be configured to use asecond timeslot portion. Interference associated with the use of thesecond timeslot portion may then be determined (e.g., based on CQIreports collected over a period of time). The network controller maythen assign the timeslot portion associated with lowest interference tothe access point.

For an uplink, an access terminal may be configured to initially use afirst timeslot portion. Interference associated with the use of thattimeslot portion may, for example, be determined indirectly based on thetransmit power values (e.g., as automatically set by power controlcommands from an associated access point) used when transmitting on theuplink over a period of time. The access terminal may then be configuredto use a second timeslot portion. Interference associated with the useof the second timeslot portion may then be determined (e.g., asdiscussed above). The network node 114 may then assign the timeslotportion associated with lowest interference (e.g., as indicated by thelowest uplink transmit power) to that access terminal and its associatedaccess point.

The network node 114 also may designate timeslot portions forneighboring nodes in a manner that mitigates interference between thenodes. As a specific example, the network node 114 may determine thatdownlink transmission by the access point 106 may interfere withreception at an access terminal associated with the access point 104.This may be determined, for example, based on the downlinkinterference-related information that the network node 114 may acquireas discussed herein. To mitigate such potential interference, thenetwork node 114 may assign different timeslot portions to the accesspoints 104 and 106.

As represented by block 906, the network node 114 may determine a timingoffset of one or more access points in order to synchronize the timeslottiming of the access points. Such synchronization may be achieved, forexample, using an adjustment such as Tau-DPCH (where DPCH relates to adedicated physical channel) or some other suitable synchronizationscheme.

As represented by block 908, the network node 114 then sends thetimeslot portion parameters it defined to one or more access points. Forexample, a network node 114 may send a node-specific designation to eachaccess point or the network node 114 may send a common designation toall of the access points in a set of access points. The network node 114also may send one or more timing offset indications to the access pointsfor use in synchronization operations.

Referring now to FIG. 10, this flowchart describes operations that maybe performed by an access point for downlink operations or an accessterminal for uplink operations. Initially, the downlink case will betreated.

As represented by block 1002, the access point 104 (e.g., a timeslotcontrol component 348 of the interference controller 322) determines thetimeslot portion it will use for downlink communication. In the eventthe network node 114 designated the timeslot portion to be used by theaccess point 104, the access point 104 may simply use these timeslotportions. In some cases, the access point 104 may randomly select whichtimeslot portion to use.

If the timeslot portion was not designated by the network node 114 orselected randomly, the access point 104 may determine which timeslotportion to use based on appropriate criteria. In some aspects, theaccess point 104 may select the timeslot portion associated with thelowest interference. Here, the access point 104 may determine whichtimeslot portion to use in a similar manner as discussed above at block904 (e.g., by using different portions over different periods of timeand monitoring CQI or some other parameter during each period of time).

In some cases, the access point 104 may cooperate with one or more otheraccess points to determine which timeslot portion to use. For example,the access point 104 and the access point 106 may negotiate to usedifferent (e.g., mutually exclusive) timeslot portions.

As represented by block 1004, the access point 104 may determine atiming offset to use for downlink communication. For example, the accesspoint 104 may continuously monitor a link over a period of time todetermine approximately when a neighboring node commences and ends itstransmissions. In this way, the access point 104 may determine (e.g.,estimate) the timeslot portion timing of the neighboring node. Theaccess point may then synchronize the timeslot timing portion of itsdownlink to that time. In some aspects this may be involve defining aTau-DPCH parameter.

As represented by block 1006, the access point 104 may send a message(e.g., including timing offset information) to an associated accessterminal to inform the access terminal which timeslot portions are to beused for the downlink. In this way, the access point 104 may scheduledownlink transmissions on the best available timeslot portions (block1008).

Turning now to the uplink scenario, as represented by block 1002, theaccess terminal 110 (e.g., the interference controller 324) determinesthe timeslot portions it will use for uplink communication. In the eventthe network node 114 designated the timeslot portions to be used by theaccess terminal 110, the access terminal 110 may simply use thesetimeslot portions. In some cases, the access terminal 110 may randomlyselect which timeslot portion to use.

If the timeslot portions were not designated by the network node 114 orselected randomly, the access terminal 110 may determine which timeslotportion to use based on appropriate criteria. In some aspects, theaccess terminal 110 may select the timeslot portion associated with thelowest interference (e.g., lowest transmit power). Here, the accessterminal 110 may determine which timeslot portion to use in a similarmanner as discussed above at block 904 or this may occur automaticallydue to the power control operations of the access point 104.

In some cases, the access point 104 may monitor uplink interferenceduring a timeslot portion test (e.g., a test to determine which timeslotportion has the lowest interference). In such cases, the access point104 may instruct the access terminal 110 to use certain timeslot potionsduring a given phase of the interference test. Alternatively, the accessterminal 110 may tell the access point 104 which timeslot portions arebeing used for a given phase of the test.

In some cases, the access point 104 may cooperate with one or more otheraccess points to determine which uplink timeslot portion to use. Forexample, the access point 104 and the access point 106 may negotiate touse different (e.g., mutually exclusive) timeslot portions. In such acase, the access point 104 may forward this information to the accessterminal 110.

As represented by block 1004, the access terminal 110 may determine atiming offset to use for uplink or downlink communication. For example,the access terminal 110 may continuously monitor a link over a period oftime to determine approximately when a neighboring node commences andends its transmissions. In this way, the access terminal 110 maydetermine (e.g., estimate) the timeslot portion timing of theneighboring node. Alternatively, the access terminal 110 may receivetiming offset information from the access point 104 (e.g., a Tau-DPCHparameter). In either case, the access terminal 110 may then synchronizethe timeslot timing portion of its uplink to that time.

As represented by block 1006, the access terminal 110 may send a messageto the access point 104 to inform the access point 104 which timeslotportions are to be used for the uplink. In this way, the access terminal110 may schedule uplink data transmissions on the best availabletimeslot portions (block 1008).

The above operations may be performed on a repeated based in an attemptto continually provide the best timeslot portions for the nodes in thesystem. In some cases, a decision may be made to not transmit duringcertain pilot bit times to provide a more accurate SNR estimate (e.g.,for EV-DO). In some cases, a decision may be made to not transmit duringcertain overhead channels to provide better isolation (e.g., for HSPA).In addition, provisions may be made at access terminals to account forthe lower signal measurements they may see from access points employingthe above scheme.

Referring now to FIGS. 11 and 12, operations relating to the use of afractional reuse scheme employing spectral masks on an uplink or adownlink will be described in more detail. In some aspects, such ascheme may involve configuring neighboring nodes (e.g., access pointsand/or access terminals) to use different spectral masks whentransmitting. Here, instead of utilizing all of the available frequencyspectrum at constant power, each node may utilize a spectral mask tocreate a non-uniform power spectral density. For example, a first accesspoint may transmit using a spectral mask associated with a first set ofspectral components (e.g., a first subset of an allocated frequencyspectrum) while a second access point transmits using another spectralmask associated with a second set of spectral components (e.g., a secondsubset of an allocated frequency spectrum). As a result, interferencethat may otherwise occur between the nodes may be reduced.

In some aspects, a determination as to whether a node will use a givenspectral mask may involve determining how much interference is seen whendifferent spectral masks are used. For example, a node may elect to usea spectral mask that is associated with lower interference. Here, itshould be appreciated that a given spectral mask may be defined toinclude spectral components that are not contiguous in frequency or maybe defined as a single contiguous range of frequencies. Also, a spectralmask may comprise a positive mask (e.g., defining frequency componentsto be used) or a negative mask (e.g., defining frequency components notto be used).

Referring initially to FIG. 11, as represented by block 1102, thenetwork node 114 (e.g., a spectral mask control component 350 of theinterference controller 320) may receive information that is indicativeof the interference associated with different spectral components of afrequency spectrum allocated for uplink or downlink transmission.

The operations of block 1102 may therefore be based oninterference-related feedback from one or more access points and/oraccess terminals in the system (e.g. as discussed above). For example,access terminal measurement reports and/or reports from access nodes maybe used to determine the extent to which the nodes in the system mayinterfere with one another when a given spectral mask is used.

As represented by block 1104, in some cases the network node 114 mayspecify specific spectral masks to be used by specific nodes. In somecases the spectral masks may be assigned in a random manner. Typically,however, the spectral masks may be selected in an effort to moreeffectively mitigate interference between nodes in the system.

For example, for a downlink, an access point may first be configured touse a first spectral mask (e.g., a filter defined with certain spectralcharacteristics) when transmitting. This spectral mask may berestricted, for example, to substantially the first half of theallocated spectrum (e.g., the spectral mask has substantially full powerspectral density for half of the spectrum and significantly reducedpower spectral density for the other half of the spectrum). Interferenceassociated with the use of that spectral mask may then be determined(e.g., based on CQI reports collected over a period of time). The accesspoint may then be configured to use a second spectral mask (e.g., thatis restricted to substantially the second half of the allocatedspectrum). Interference associated with the use of the second spectralmask may then be determined (e.g., based on CQI reports collected over aperiod of time). The network node 114 may then assign the spectral maskassociated with lowest interference to the access point.

For an uplink, an access terminal may first be configured to use a firstspectral mask when transmitting. Interference associated with the use ofthat spectral mask may then be determined (e.g., based on uplinkinterference measured by an associated access terminal). The accessterminal may then be configured to use a second spectral mask andinterference associated with the use of the second spectral mask isdetermined. The network node 114 may then assign the spectral maskassociated with lowest interference to the access terminal.

The network node 114 also may designate spectral masks for neighboringnodes in a manner that mitigates interference between the nodes. As aspecific example, the network node 114 may determine that downlinktransmission by the access point 106 may interfere with reception at anaccess terminal associated with the access point 104. This may bedetermined, for example, based on the downlink interference-relatedinformation that the network node 114 may acquire as discussed herein.To mitigate such potential interference, the network node 114 may assigndifferent spectral masks to the access points 104 and 106.

As represented by block 1106, the network node 114 then sends thespectral masks it identified to the appropriate access point(s). Here,the network node 114 may send a node-specific message to each accesspoint or the network node 114 may send a common message to all of theaccess points in a set of access points.

Referring now to FIG. 12, this flowchart describes operations that maybe performed by an access point and an associated access terminal foruplink and downlink operations. As represented by block 1202, the accesspoint 104 (e.g., a spectral mask control component 352 of theinterference controller 322) determines the spectral mask that will beused for the uplink or the downlink. In the event the network node 114designated the spectral mask to be used, the access point 104 may simplyuse the designated spectral mask. In some cases, the access point 104may randomly select which spectral mask to use.

If the spectral mask was not designated by the network node 114 orselected randomly, the access point 104 may determine which spectralmask to use based on appropriate criteria. In some aspects, the accesspoint 104 may select the spectral mask associated with the lowestinterference. For example, the access point 104 may determine whichspectral mask to use in a similar manner as discussed above at blocks1102 and 1104 (e.g., through the use of different spectral masks overdifferent periods of time and monitoring CQI or some otherinterference-related parameter during each period of time).

In some cases, the access point 104 may cooperate with one or more otheraccess points to determine which spectral mask to use. For example, theaccess point 104 and the access point 106 may negotiate to use different(e.g., mutually exclusive) spectral masks.

As represented by block 1204, the access point 104 sends a message tothe access terminal 110 to inform the access terminal 110 which spectralmask is to be used for the uplink (or, optionally, the downlink). Inthis way, the access point 104 may transmit on the downlink using thebest available spectrum and/or the access terminal 110 may transmit onthe uplink using the best available spectrum (block 1206). Here, anequalizer at the receiving node (e.g., the access terminal for thedownlink) may mitigate the effect of the spectral mask (especially ifthere is no loading from a neighboring cell). In addition, in comecases, the equalizer may be adaptive and take into account the specificspectral mask employed at the transmitting node (e.g., the access pointfor the downlink).

The above operations may be performed on a repeated basis in an attemptto continually provide the best spectral masks for the nodes in thesystem.

Referring now to FIGS. 13 and 14, operations relating to the use of afractional reuse scheme employing spreading codes (e.g., Walsh codes orOVSF codes) are described. In some aspects, such a scheme may involveconfiguring neighboring nodes (e.g., access points) to use differentspreading codes when transmitting. Here, instead of utilizing all of thecodes in an allocated set of spreading codes, each node may utilize asubset of the spreading codes. For example, a first access point maytransmit using a first set of spreading codes while a second accesspoint transmits using a second set of spreading codes. As a result,interference that may otherwise occur between the nodes may be reduced.

In some aspects, a determination as to whether a node will use a givenspreading code may involve determining how much interference is seenwhen different spreading codes are used. For example, a node may electto use a spreading code that is associated with lower interference.

Referring initially to FIG. 13, as represented by block 1302, thenetwork node 114 (e.g., a spreading code control component 354 of theinterference controller 320) may receive information that is indicativeof the interference associated with different spreading code subsets ofa set of spreading codes allocated for downlink transmission.

The operations of block 1302 may therefore be based oninterference-related feedback from one or more access points and/oraccess terminals in the system (e.g., as discussed above). For example,access terminal measurement reports and/or reports from access nodes maybe used to determine the extent to which the nodes in the system mayinterfere with one another when a given spreading code is used.

As represented by block 1304, in some cases the network node 114 mayspecify specific spreading codes to be used by specific nodes. In somecases the spreading codes may be assigned in a random manner. Typically,however, the spreading codes may be selected in an effort to moreeffectively mitigate interference between nodes in the system.

For example, an access point may first be configured to use a first setof spreading codes when transmitting on a downlink. Interferenceassociated with the use of that set of spreading codes may then bedetermined (e.g., based on CQI reports collected over a period of time).The access point may then be configured to use a second set of spreadingcodes and interference associated with the use of the second set ofspreading codes is determined. The network node 114 may then assign thespreading code associated with lowest interference to the access point.

The network node 114 also may designate spreading codes for neighboringnodes in a manner that mitigates interference between the nodes. As aspecific example, the network node 114 may determine that downlinktransmission by the access point 104 may interfere with reception at anaccess terminal associated with the access point 106. This may bedetermined, for example, based on the downlink interference-relatedinformation that the network node 114 may acquire as discussed herein.To mitigate such potential interference, the network node 114 may assigndifferent spreading codes to the access points 104 and 106.

As represented by block 1306, the network node 114 then sends thespreading codes it identified to the appropriate access point(s). Here,the network node 114 may send a node-specific message to each accesspoint or the network node 114 may send a common message to all of theaccess points in a set of access points.

As represented by block 1308, the network node 114 also may send one ormore other sets of spreading codes to the access point(s). As will bediscussed in more detail below, these sets may identify the spreadingcodes that are not being used by a given access point and/or thespreading codes that are being used by some other access point.

Referring now to FIG. 14, as represented by block 1402, the access point104 (e.g., a spreading code control component 356 of the interferencecontroller 322) determines the set of spreading codes that will be usedfor the downlink. In the event the network node 114 designated the setto be used, the access point 104 may simply use the designated set. Insome cases, the access point 104 may randomly select which set ofspreading codes to use.

If the set of spreading codes was not designated by the network node 114or selected randomly, the access point 104 may determine which set touse based on appropriate criteria. In some aspects, the access point 104may select the set of spreading codes associated with the lowestinterference. For example, the access point 104 may determine which setto use in a similar manner as discussed above at blocks 1302 and 1304(e.g., through the use of different spreading codes over differentperiods of time and monitoring CQI or some other interference-relatedparameter during each period of time).

In some cases, the access point 104 may cooperate with one or more otheraccess points to determine which set of spreading codes to use. Forexample, the access point 104 and the access point 106 may negotiate touse a different (e.g., mutually exclusive) set of spreading codes.

As represented by block 1404, the access point 104 may optionallysynchronize its timing with the timing of one or more other accesspoints. For example, by achieving chip alignment with neighboring cells(e.g., associated with other restricted access points), orthogonalchannels may be established between the access points through the use ofdifferent spreading codes at each access point. Such synchronization maybe accomplished, for example, using techniques as described above (e.g.,the access points may include GPS functionality).

As represented by block 1406, the access point 104 may optionallydetermine the spreading codes that are used by one or more other accesspoints. Such information be acquired, for example, from the network node114 or directly from the other access nodes (e.g., via the backhaul).

As represented by block 1408, the access point 104 sends a message tothe access terminal 110 to inform the access terminal 110 whichspreading code is to be used for the downlink. In addition, the accesspoint 104 may send information to the access terminal 110 thatidentifies the spreading codes that are not being used by the accesspoint 104 and/or that identifies the spreading codes that are being usedby some other access point (e.g., a neighboring access point).

As represented by block 1410, the access point 104 transmits on thedownlink using the selected set of spreading codes. In addition, asrepresented by block 1412, the access terminal 110 uses the spreadingcode information sent by the access point 104 to decode the informationit receives via the downlink.

In some implementations, the access terminal 110 may be configured toutilize the information regarding the spreading codes not used by theaccess point 104 to more efficiently decode the received information.For example, a signal processor 366 (e.g., comprising interferencecancellation capabilities) may use these other spreading codes in anattempt to cancel, from the received information, any interferencecreated by signals received from another node (e.g., the access point106) that were encoded using these other spreading codes. Here, theoriginal received information is operated on using the other spreadingcodes to provide decoded bits. A signal is then generated from thedecoded bits and this signal is subtracted from the original receivedinformation. The resulting signal is then operated on using thespreading codes sent by the access point 104 to provide an outputsignal. Advantageously, through the use of such interference controltechniques, relatively high levels of interference rejection may beachieved even when the access point 104 and the access terminal 110 arenot time synchronized.

The above operations may be performed on a repeated based in an attemptto continually provide the best spreading codes for the nodes in thesystem.

Referring now to FIGS. 15 and 16, operations relating to the use of apower control-related scheme for mitigating interference will bedescribed. In particular, these operations relate to controlling thetransmit power of an access terminal to mitigate any interference theaccess terminal may cause on the uplink at a non-associated access point(e.g., that is operating on the same carrier frequency of an adjacentcarrier frequency).

As represented by block 1502, a node (e.g., the network node 114 or theaccess point 104) receives power control-related signals that may beused to determine how to control the uplink transmit power of the accessterminal 110. In various scenarios, the signals may be received from thenetwork node 114, the access point 104, another access point (e.g.,access point 106), or an associated access terminal (e.g., accessterminal 110). Such information may be received in various ways (e.g.,over a backhaul, over the air, etc.).

In some aspects, these received signals may provide an indication ofinterference at a neighboring access point (e.g., access point 106). Forexample, as discussed herein the access terminals associated with theaccess point 104 may generate measurement reports and send in thesereports to the network node 114 via the access point 104.

In addition, access points in the system may generate a load indication(e.g., a busy bit or a relative grant channel) and send this informationto its associated access terminal via a downlink. Thus, the access point104 may monitor the downlink to acquire this information or the accesspoint 104 may acquire this information from its associated accessterminals that may receive this information over the downlink.

In some cases interference information may be received from the networknode 114 or the access point 106 via the backhaul. For example, theaccess point 106 may report its loading (e.g., interference) informationto the network node 114. The network node 114 may then distribute thisinformation to other access points in the system. In addition, theaccess points in the system may communicate directly with one another toinform each other of their respective loading conditions.

As represented by block 1504, a transmit power indication for the accessterminal 110 is defined based on the above parameters. This indicationmay relate to, for example, a maximum allowed power value, aninstantaneous power value, or a traffic-to-pilot (T2P) indication.

In some aspects, a maximum transmit power value for the access terminal110 is defined by estimating the interference the access terminal 110may induce at the access point 106. This interference may be estimated,for example, based on path loss information derived from the measurementreports received from the access terminal 110. For example, the accessterminal 110 may determine the path loss to the access point 106 in thepath loss to the access point 104. Based on this information, the accesspoint 104 may determine the power being induced (e.g., the amount ofinterference) at the access point 106 based on the signal strength ofthe signals the access point 104 receives from the access terminal 110.The access point 104 may thus determine the maximum allowed transmitpower for access terminal 110 based on the above measurements (e.g., themaximum transmit power may be reduced by a certain amount).

In some aspects, an instantaneous power value may be generated tocontrol the current transmit power of the access terminal. For example,in the event the amount of induced interference is greater than or equalto a threshold value, the access terminal 110 may be instructed toreduce its transmit power (e.g., by a specific amount or to a specifiedvalue).

In some cases, a power control operation may be based on one or moreparameters. For example, if the access point 104 receives a busy bitfrom the access point 106, the access point 104 may utilize informationfrom the measurement reports to determine whether the interference atthe access point 106 is being caused by the access terminal 110.

Referring now to FIG. 16, in some implementations the transmit powerindication generate a block 1504 may relate to maximum uplink T2P.Moreover, in some cases this value may be defined as a function of thedownlink SINR. The waveform 1602 of FIG. 16 illustrates one example of afunction that relates downlink SINR to uplink T2P. In this case, theuplink T2P application may be decreased as the downlink SINR decreases.In this way, uplink interference from access terminals in linkunbalanced may be limited. As shown in example of FIG. 16, a minimum T2Pvalue 1604 may be defined for the access terminal such that a certainamount of minimum weight is guaranteed. In addition, a maximum T2P value1606 may be defined. In some aspects, the uplink T2P allocated to eachaccess terminal may be limited by the minimum of the access terminal'spower headroom or a function based on downlink SINR (e.g., as shown inFIG. 16). In some implementations (e.g., 3GPP), the above functionalitymay be provided by the uplink scheduler an access point that has accessto CQI feedback from an access terminal.

Referring again to FIG. 15, as represented by block 1506, in someimplementations the rise-over-thermal (“RoT”) threshold for an accesspoint may be allowed to increase above a conventional value for loadcontrol purposes. For example, in some cases no limit may be placed onthe RoT threshold. In some cases, the RoT threshold may be allowed torise to a value limited only by the uplink link budget or a saturationlevel at the access point. For example, an upper threshold RoT may beincreased in the access point 104 to a predetermined value to enableeach associated access terminal to operate at the highest T2P levelallowed by its power headroom.

By allowing such an increase in the RoT threshold, the access point maycontrol its total received signal strength. This may prove advantageousunder situations where the access point is experiencing high level ofinterference (e.g., from nearby access terminal). In the absence of anRoT threshold limit, however, the access terminals in neighboring cellsmay get into a power race to overcome the interference from one another.For example, these access terminals may saturate at their maximum uplinktransmit power (e.g., 23 dBm) and, as a result, may cause significantinterference at macro access points. To prevent such a race condition,the transmit power of the access terminal may be reduced as a result ofan increase in the RoT threshold. In some cases, such a race conditionmay be avoided through the use of a maximum uplink T2P control scheme(e.g., as described above in conjunction with FIG. 16).

As represented by block 1508, an indication of a transmit power value(e.g., maximum power, an instantaneous power, or T2P) as calculatedusing one or more of the techniques described above may be sent to theaccess terminal 110 to control the transmit power of the access terminal110. Such a message may be sent directly or indirectly. As an example ofthe former case, explicit signaling may be used to inform the accessterminal 110 of the new maximum power value. As an example of the lattercase, the access point 104 may adjust T2P or may forward a loadindication from the access point 106 (possibly after some modification)to the access terminal 110. The access terminal 110 may then use thisparameter to determine the maximum power value.

Referring now to FIG. 17, in some implementations a signal attenuationfactor may be adjusted to mitigate interference. Such a parameter maycomprise a noise figure or attenuation. The amount of such padding orsignal attenuation may be dynamically adjusted based on signal strengthmeasured from other nodes (e.g., as discussed herein) or certainsignaling messages (e.g., indicative of interference) exchanged betweenaccess points. In this way, the access point 104 may compensate forinterference induced by nearby access terminals.

As represented by block 1702, the access terminal 108 may receive powercontrol-related signals (e.g., as discussed above). As represented byblocks 1704 and 1706, the access point 104 may determine whether thereceived signal strength from an associated access terminal or anon-associated access terminal is greater than or equal to a thresholdlevel. If not, the access point 104 continues monitoring power controlrelated-signals. If so, the access point 104 adjusts the attenuationfactor at block 1708. For example, in response to an increase inreceived signal strength, the access point 104 may increase its noisefigure or receiver attenuation. As represented by block 1710, the accesspoint 104 may send a transmit power control message to its associatedaccess terminals to increase their uplink transmit power as a result ofthe increase in the attenuation factor (e.g., to overcome the noisefigure or the uplink attenuation placed on the access point 104).

In some aspects, the access point 104 may distinguish the signalsreceived from non-associated access terminals from the signals receivedfrom associated access terminals. In this way, the access terminal 108may make an appropriate adjustment to the transmit power of itsassociated access terminals. For example, different adjustments may bemade in response to signals from associated versus non-associated accessterminals (e.g., depending on whether there is only one associatedaccess terminal).

In another embodiment, interference cancellation may be performed by anaccess point for the access terminals that are not served by the accesspoint or for the access terminals that are not in the active set ofaccess points. For this purpose scrambling codes (in WCDMA or HSPA) oruser long codes (in 1xEV-DO) may be shared among all the access points(that receive the scrambling codes from all the access terminals).Subsequently, the access point decodes the respective access terminalinformation and removes the interference associated with the respectiveaccess terminals.

In some aspects, the teachings herein may be employed in a network thatincludes macro scale coverage (e.g., a large area cellular network suchas a 3G network, typically referred to as a macro cell network) andsmaller scale coverage (e.g., a residence-based or building-basednetwork environment). As an access terminal (“AT”) moves through such anetwork, the access terminal may be served in certain locations byaccess nodes (“ANs”) that provide macro coverage while the accessterminal may be served at other locations by access nodes that providesmaller scale coverage. In some aspects, the smaller coverage nodes maybe used to provide incremental capacity growth, in-building coverage,and different services (e.g., for a more robust user experience). In thediscussion herein, a node that provides coverage over a relatively largearea may be referred to as a macro node. A node that provides coverageover a relatively small area (e.g., a residence) may be referred to as afemto node. A node that provides coverage over an area that is smallerthan a macro area and larger than a femto area may be referred to as apico node (e.g., providing coverage within a commercial building).

A cell associated with a macro node, a femto node, or a pico node may bereferred to as a macro cell, a femto cell, or a pico cell, respectively.In some implementations, each cell may be further associated with (e.g.,divided into) one or more sectors.

In various applications, other terminology may be used to reference amacro node, a femto node, or a pico node. For example, a macro node maybe configured or referred to as an access node, base station, accesspoint, eNodeB, macro cell, and so on. Also, a femto node may beconfigured or referred to as a Home NodeB, Home eNodeB, access pointbase station, femto cell, and so on.

FIG. 18 illustrates a wireless communication system 1800, configured tosupport a number of users, in which the teachings herein may beimplemented. The system 1800 provides communication for multiple cells1802, such as, for example, macro cells 1802A-1802G, with each cellbeing serviced by a corresponding access node 1804 (e.g., access nodes1804A-1804G). As shown in FIG. 18, access terminals 1806 (e.g., accessterminals 1806A-1806L) may be dispersed at various locations throughoutthe system over time. Each access terminal 1806 may communicate with oneor more access nodes 1804 on a forward link (“FL”) and/or a reverse link(“RL) at a given moment, depending upon whether the access terminal 1806is active and whether it is in soft handoff, for example. The wirelesscommunication system 1800 may provide service over a large geographicregion. For example, macro cells 1802A-1802G may cover a few blocks in aneighborhood.

FIG. 19 illustrates an exemplary communication system 1900 where one ormore femto nodes are deployed within a network environment.Specifically, the system 1900 includes multiple femto nodes 1910 (e.g.,femto nodes 1910A and 1910B) installed in a relatively small scalenetwork environment (e.g., in one or more user residences 1930). Eachfemto node 1910 may be coupled to a wide area network 1940 (e.g., theInternet) and a mobile operator core network 1950 via a DSL router, acable modem, a wireless link, or other connectivity means (not shown).As will be discussed below, each femto node 1910 may be configured toserve associated access terminals 1920 (e.g., access terminal 1920A)and, optionally, alien access terminals 1920 (e.g., access terminal1920B). In other words, access to femto nodes 1910 may be restrictedwhereby a given access terminal 1920 may be served by a set ofdesignated (e.g., home) femto node(s) 1910 but may not be served by anynon-designated femto nodes 1910 (e.g., a neighbor's femto node 1910).

FIG. 20 illustrates an example of a coverage map 2000 where severaltracking areas 2002 (or routing areas or location areas) are defined,each of which includes several macro coverage areas 2004. Here, areas ofcoverage associated with tracking areas 2002A, 2002B, and 2002C aredelineated by the wide lines and the macro coverage areas 2004 arerepresented by the hexagons. The tracking areas 2002 also include femtocoverage areas 2006. In this example, each of the femto coverage areas2006 (e.g., femto coverage area 2006C) is depicted within a macrocoverage area 2004 (e.g., macro coverage area 2004B). It should beappreciated, however, that a femto coverage area 2006 may not lieentirely within a macro coverage area 2004. In practice, a large numberof femto coverage areas 2006 may be defined with a given tracking area2002 or macro coverage area 2004. Also, one or more pico coverage areas(not shown) may be defined within a given tracking area 2002 or macrocoverage area 2004.

Referring again to FIG. 19, the owner of a femto node 1910 may subscribeto mobile service, such as, for example, 3G mobile service, offeredthrough the mobile operator core network 1950. In addition, an accessterminal 1920 may be capable of operating both in macro environments andin smaller scale (e.g., residential) network environments. In otherwords, depending on the current location of the access terminal 1920,the access terminal 1920 may be served by an access node 1960 of themacro cell mobile network 1950 or by any one of a set of femto nodes1910 (e.g., the femto nodes 1910A and 1910B that reside within acorresponding user residence 1930). For example, when a subscriber isoutside his home, he is served by a standard macro access node (e.g.,node 1960) and when the subscriber is at home, he is served by a femtonode (e.g., node 1910A). Here, it should be appreciated that a femtonode 1910 may be backward compatible with existing access terminals1920.

A femto node 1910 may be deployed on a single frequency or, in thealternative, on multiple frequencies. Depending on the particularconfiguration, the single frequency or one or more of the multiplefrequencies may overlap with one or more frequencies used by a macronode (e.g., node 1960).

In some aspects, an access terminal 1920 may be configured to connect toa preferred femto node (e.g., the home femto node of the access terminal1920) whenever such connectivity is possible. For example, whenever theaccess terminal 1920 is within the user's residence 1930, it may bedesired that the access terminal 1920 communicate only with the homefemto node 1910.

In some aspects, if the access terminal 1920 operates within the macrocellular network 1950 but is not residing on its most preferred network(e.g., as defined in a preferred roaming list), the access terminal 1920may continue to search for the most preferred network (e.g., thepreferred femto node 1910) using a Better System Reselection (“BSR”),which may involve a periodic scanning of available systems to determinewhether better systems are currently available, and subsequent effortsto associate with such preferred systems. With the acquisition entry,the access terminal 1920 may limit the search for specific band andchannel. For example, the search for the most preferred system may berepeated periodically. Upon discovery of a preferred femto node 1910,the access terminal 1920 selects the femto node 1910 for camping withinits coverage area.

A femto node may be restricted in some aspects. For example, a givenfemto node may only provide certain services to certain accessterminals. In deployments with so-called restricted (or closed)association, a given access terminal may only be served by the macrocell mobile network and a defined set of femto nodes (e.g., the femtonodes 1910 that reside within the corresponding user residence 1930). Insome implementations, a node may be restricted to not provide, for atleast one node, at least one of: signaling, data access, registration,paging, or service.

In some aspects, a restricted femto node (which may also be referred toas a Closed Subscriber Group Home NodeB) is one that provides service toa restricted provisioned set of access terminals. This set may betemporarily or permanently extended as necessary. In some aspects, aClosed Subscriber Group (“CSG”) may be defined as the set of accessnodes (e.g., femto nodes) that share a common access control list ofaccess terminals. A channel on which all femto nodes (or all restrictedfemto nodes) in a region operate may be referred to as a femto channel.

Various relationships may thus exist between a given femto node and agiven access terminal. For example, from the perspective of an accessterminal, an open femto node may refer to a femto node with norestricted association. A restricted femto node may refer to a femtonode that is restricted in some manner (e.g., restricted for associationand/or registration). A home femto node may refer to a femto node onwhich the access terminal is authorized to access and operate on. Aguest femto node may refer to a femto node on which an access terminalis temporarily authorized to access or operate on. An alien femto nodemay refer to a femto node on which the access terminal is not authorizedto access or operate on, except for perhaps emergency situations (e.g.,911 calls).

From a restricted femto node perspective, a home access terminal mayrefer to an access terminal that is authorized to access the restrictedfemto node. A guest access terminal may refer to an access terminal withtemporary access to the restricted femto node. An alien access terminalmay refer to an access terminal that does not have permission to accessthe restricted femto node, except for perhaps emergency situations, forexample, such as 911 calls (e.g., an access terminal that does not havethe credentials or permission to register with the restricted femtonode).

For convenience, the disclosure herein describes various functionalityin the context of a femto node. It should be appreciated, however, thata pico node may provide the same or similar functionality for a largercoverage area. For example, a pico node may be restricted, a home piconode may be defined for a given access terminal, and so on.

A wireless multiple-access communication system may simultaneouslysupport communication for multiple wireless access terminals. Asmentioned above, each terminal may communicate with one or more basestations via transmissions on the forward and reverse links. The forwardlink (or downlink) refers to the communication link from the basestations to the terminals, and the reverse link (or uplink) refers tothe communication link from the terminals to the base stations. Thiscommunication link may be established via a single-in-single-out system,a multiple-in-multiple-out (“MIMO”) system, or some other type ofsystem.

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, which are also referred to as spatialchannels, where N_(S)≦min{N_(T), N_(R)}. Each of the N_(S) independentchannels corresponds to a dimension. The MIMO system may provideimproved performance (e.g., higher throughput and/or greaterreliability) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

A MIMO system may support time division duplex (“TDD”) and frequencydivision duplex (“FDD”). In a TDD system, the forward and reverse linktransmissions are on the same frequency region so that the reciprocityprinciple allows the estimation of the forward link channel from thereverse link channel. This enables the access point to extract transmitbeam-forming gain on the forward link when multiple antennas areavailable at the access point.

The teachings herein may be incorporated into a node (e.g., a device)employing various components for communicating with at least one othernode. FIG. 21 depicts several sample components that may be employed tofacilitate communication between nodes. Specifically, FIG. 21illustrates a wireless device 2110 (e.g., an access point) and awireless device 2150 (e.g., an access terminal) of a MIMO system 2100.At the device 2110, traffic data for a number of data streams isprovided from a data source 2112 to a transmit (“TX”) data processor2114.

In some aspects, each data stream is transmitted over a respectivetransmit antenna. The TX data processor 2114 formats, codes, andinterleaves the traffic data for each data stream based on a particularcoding scheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot datausing OFDM techniques. The pilot data is typically a known data patternthat is processed in a known manner and may be used at the receiversystem to estimate the channel response. The multiplexed pilot and codeddata for each data stream is then modulated (i.e., symbol mapped) basedon a particular modulation scheme (e.g., BPSK, QSPK, M-PSK, or M-QAM)selected for that data stream to provide modulation symbols. The datarate, coding, and modulation for each data stream may be determined byinstructions performed by a processor 2130. A data memory 2132 may storeprogram code, data, and other information used by the processor 2130 orother components of the device 2110.

The modulation symbols for all data streams are then provided to a TXMIMO processor 2120, which may further process the modulation symbols(e.g., for OFDM). The TX MIMO processor 2120 then provides N_(T)modulation symbol streams to N_(T) transceivers (“XCVR”) 2122A through2122T. In some aspects, the TX MIMO processor 2120 applies beam-formingweights to the symbols of the data streams and to the antenna from whichthe symbol is being transmitted.

Each transceiver 2122 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transceivers 2122A through 2122T are thentransmitted from N_(T) antennas 2124A through 2124T, respectively.

At the device 2150, the transmitted modulated signals are received byN_(R) antennas 2152A through 2152R and the received signal from eachantenna 2152 is provided to a respective transceiver (“XCVR”) 2154Athrough 2154R. Each transceiver 2154 conditions (e.g., filters,amplifies, and downconverts) a respective received signal, digitizes theconditioned signal to provide samples, and further processes the samplesto provide a corresponding “received” symbol stream.

A receive (“RX”) data processor 2160 then receives and processes theN_(R) received symbol streams from N_(R) transceivers 2154 based on aparticular receiver processing technique to provide N_(T) “detected”symbol streams. The RX data processor 2160 then demodulates,deinterleaves, and decodes each detected symbol stream to recover thetraffic data for the data stream. The processing by the RX dataprocessor 2160 is complementary to that performed by the TX MIMOprocessor 2120 and the TX data processor 2114 at the device 2110.

A processor 2170 periodically determines which pre-coding matrix to use(discussed below). The processor 2170 formulates a reverse link messagecomprising a matrix index portion and a rank value portion. A datamemory 2172 may store program code, data, and other information used bythe processor 2170 or other components of the device 2150.

The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 2138,which also receives traffic data for a number of data streams from adata source 2136, modulated by a modulator 2180, conditioned by thetransceivers 2154A through 2154R, and transmitted back to the device2110.

At the device 2110, the modulated signals from the device 2150 arereceived by the antennas 2124, conditioned by the transceivers 2122,demodulated by a demodulator (“DEMOD”) 2140, and processed by an RX dataprocessor 2142 to extract the reverse link message transmitted by thedevice 2150. The processor 2130 then determines which pre-coding matrixto use for determining the beam-forming weights and then processes theextracted message.

FIG. 21 also illustrates that the communication components may includeone or more components that perform interference control operations astaught herein. For example, an interference (“INTER.”) control component2190 may cooperate with the processor 2130 and/or other components ofthe device 2110 to send/receive signals to/from another device (e.g.,device 2150) as taught herein. Similarly, an interference controlcomponent 2192 may cooperate with the processor 2170 and/or othercomponents of the device 2150 to send/receive signals to/from anotherdevice (e.g., device 2110). It should be appreciated that for eachdevice 2110 and 2150 the functionality of two or more of the describedcomponents may be provided by a single component. For example, a singleprocessing component may provide the functionality of the interferencecontrol component 2190 and the processor 2130 and a single processingcomponent may provide the functionality of the interference controlcomponent 2192 and the processor 2170.

The teachings herein may be incorporated into various types ofcommunication systems and/or system components. In some aspects, theteachings herein may be employed in a multiple-access system capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., by specifying one or more of bandwidth, transmitpower, coding, interleaving, and so on). For example, the teachingsherein may be applied to any one or combinations of the followingtechnologies: Code Division Multiple Access (“CDMA”) systems,Multiple-Carrier CDMA (“MCCDMA”), Wideband CDMA (“W-CDMA”), High-SpeedPacket Access (“HSPA,” “HSPA+”) systems, Time Division Multiple Access(“TDMA”) systems, Frequency Division Multiple Access (“FDMA”) systems,Single-Carrier FDMA (“SC-FDMA”) systems, Orthogonal Frequency DivisionMultiple Access (“OFDMA”) systems, or other multiple access techniques.A wireless communication system employing the teachings herein may bedesigned to implement one or more standards, such as IS-95, cdma2000,IS-856, W-CDMA, TDSCDMA, and other standards. A CDMA network mayimplement a radio technology such as Universal Terrestrial Radio Access(“UTRA)”, cdma2000, or some other technology. UTRA includes W-CDMA andLow Chip Rate (“LCR”). The cdma2000 technology covers IS-2000, IS-95 andIS-856 standards. A TDMA network may implement a radio technology suchas Global System for Mobile Communications (“GSM”). An OFDMA network mayimplement a radio technology such as Evolved UTRA (“E-UTRA”), IEEE802.11, IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, andGSM are part of Universal Mobile Telecommunication System (“UMTS”). Theteachings herein may be implemented in a 3GPP Long Term Evolution(“LTE”) system, an Ultra-Mobile Broadband (“UMB”) system, and othertypes of systems. LTE is a release of UMTS that uses E-UTRA. Althoughcertain aspects of the disclosure may be described using 3GPPterminology, it is to be understood that the teachings herein may beapplied to 3GPP (Re199, Re15, Re16, Re17) technology, as well as 3GPP2(IxRTT, 1xEV-DO Re1O, RevA, RevB) technology and other technologies.

The teachings herein may be incorporated into (e.g., implemented withinor performed by) a variety of apparatuses (e.g., nodes). In someaspects, a node (e.g., a wireless node) implemented in accordance withthe teachings herein may comprise an access point or an access terminal.

For example, an access terminal may comprise, be implemented as, orknown as user equipment, a subscriber station, a subscriber unit, amobile station, a mobile, a mobile node, a remote station, a remoteterminal, a user terminal, a user agent, a user device, or some otherterminology. In some implementations an access terminal may comprise acellular telephone, a cordless telephone, a session initiation protocol(“SIP”) phone, a wireless local loop (“WLL”) station, a personal digitalassistant (“PDA”), a handheld device having wireless connectioncapability, or some other suitable processing device connected to awireless modem. Accordingly, one or more aspects taught herein may beincorporated into a phone (e.g., a cellular phone or smart phone), acomputer (e.g., a laptop), a portable communication device, a portablecomputing device (e.g., a personal data assistant), an entertainmentdevice (e.g., a music device, a video device, or a satellite radio), aglobal positioning system device, or any other suitable device that isconfigured to communicate via a wireless medium.

An access point may comprise, be implemented as, or known as a NodeB, aneNodeB, a radio network controller (“RNC”), a base station (“BS”), aradio base station (“RBS”), a base station controller (“BSC”), a basetransceiver station (“BTS”), a transceiver function (“TF”), a radiotransceiver, a radio router, a basic service set (“BSS”), an extendedservice set (“ESS”), or some other similar terminology.

In some aspects a node (e.g., an access point) may comprise an accessnode for a communication system. Such an access node may provide, forexample, connectivity for or to a network (e.g., a wide area networksuch as the Internet or a cellular network) via a wired or wirelesscommunication link to the network. Accordingly, an access node mayenable another node (e.g., an access terminal) to access a network orsome other functionality. In addition, it should be appreciated that oneor both of the nodes may be portable or, in some cases, relativelynon-portable.

Also, it should be appreciated that a wireless node may be capable oftransmitting and/or receiving information in a non-wireless manner(e.g., via a wired connection). Thus, a receiver and a transmitter asdiscussed herein may include appropriate communication interfacecomponents (e.g., electrical or optical interface components) tocommunicate via a non-wireless medium.

A wireless node may communicate via one or more wireless communicationlinks that are based on or otherwise support any suitable wirelesscommunication technology. For example, in some aspects a wireless nodemay associate with a network. In some aspects the network may comprise alocal area network or a wide area network. A wireless device may supportor otherwise use one or more of a variety of wireless communicationtechnologies, protocols, or standards such as those discussed herein(e.g., CDMA, TDMA, OFDM, OFDMA, WiMAX, Wi-Fi, and so on). Similarly, awireless node may support or otherwise use one or more of a variety ofcorresponding modulation or multiplexing schemes. A wireless node maythus include appropriate components (e.g., air interfaces) to establishand communicate via one or more wireless communication links using theabove or other wireless communication technologies. For example, awireless node may comprise a wireless transceiver with associatedtransmitter and receiver components that may include various components(e.g., signal generators and signal processors) that facilitatecommunication over a wireless medium.

The components described herein may be implemented in a variety of ways.Referring to FIGS. 22-30, apparatuses 2200, 2300, 2400, 2500, 2600,2700, 2800, 2900, and 3000 are represented as a series of interrelatedfunctional blocks. In some aspects the functionality of these blocks maybe implemented as a processing system including one or more processorcomponents. In some aspects the functionality of these blocks may beimplemented using, for example, at least a portion of one or moreintegrated circuits (e.g., an ASIC). As discussed herein, an integratedcircuit may include a processor, software, other related components, orsome combination thereof. The functionality of these blocks also may beimplemented in some other manner as taught herein. In some aspects oneor more of the dashed blocks in FIGS. 22-23 are optional.

The apparatuses 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, and 3000may include one or more modules that may perform one or more of thefunctions described above with regard to various figures. In someaspects, one or more components of the interference controller 320 orthe interference controller 322 may provide functionality relating to,for example, a HARQ interlace means 2202, a profile specification means2302, a phase offset means 2402, an identifying means 2502, a spectralmask means 2602, a spreading code means 2702, a processing means 2804, atransmit power means 2902, or an attenuation factor means 3004. In someaspects, the communication controller 326 or the communicationcontroller 328 may provide functionality relating to, for example, means2204, 2304, 2404, 2504, 2604, 2704, or 2904. In some aspects, the timingcontroller 332 or the timing controller 334 may provide functionalityrelating to, for example, timing means 2206, 2506, or 2706. In someaspects, the communication controller 330 may provide functionalityrelating to, for example, the receiving means 2802. In some aspects, thesignal processor 366 may provide functionality relating to, for example,the processing means 2804. In some aspects, the transceiver 302 or thetransceiver 304 may provide functionality relating to, for example, thesignal determining means 3002.

It should be understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not generallylimit the quantity or order of those elements. Rather, thesedesignations may be used herein as a convenient method of distinguishingbetween two or more elements or instances of an element. Thus, areference to first and second elements does not mean that only twoelements may be employed there or that the first element must precedethe second element in some manner. Also, unless stated otherwise a setof elements may comprise one or more elements.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that any of the variousillustrative logical blocks, modules, processors, means, circuits, andalgorithm steps described in connection with the aspects disclosedherein may be implemented as electronic hardware (e.g., a digitalimplementation, an analog implementation, or a combination of the two,which may be designed using source coding or some other technique),various forms of program or design code incorporating instructions(which may be referred to herein, for convenience, as “software” or a“software module”), or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the aspects disclosed herein may be implementedwithin or performed by an integrated circuit (“IC”), an access terminal,or an access point. The IC may comprise a general purpose processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, electrical components, optical components,mechanical components, or any combination thereof designed to performthe functions described herein, and may execute codes or instructionsthat reside within the IC, outside of the IC, or both. A general purposeprocessor may be a microprocessor, but in the alternative, the processormay be any conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

It is understood that any specific order or hierarchy of steps in anydisclosed process is an example of a sample approach. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the processes may be rearranged while remaining within thescope of the present disclosure. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

The functions described may be implemented in hardware, software,firmware, or any combination thereof. If implemented in software, thefunctions may be stored on or transmitted over as one or moreinstructions or code on a computer-readable medium. Computer-readablemedia includes both computer storage media and communication mediaincluding any medium that facilitates transfer of a computer programfrom one place to another. A storage media may be any available mediathat can be accessed by a computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media. In summary, it should be appreciated that acomputer-readable medium may be implemented in any suitablecomputer-program product.

The previous description of the disclosed aspects is provided to enableany person skilled in the art to make or use the present disclosure.Various modifications to these aspects will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other aspects without departing from the scope of thedisclosure. Thus, the present disclosure is not intended to be limitedto the aspects shown herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

What is claimed is:
 1. A method of communication, comprising: defining atransmit power profile, wherein the transmit power profile specifies howtransmit power is varied over time, and wherein the transmit powerprofile is periodic; defining maximum and minimum power levels for thetransmit power profile; defining a time period for the transmit powerprofile; sending at least one indication of the transmit power profileto a plurality of access points, wherein at least a portion of theaccess points are neighboring access points: specifying differenttransmit power profile phase offset values for different ones of theneighboring access points to mitigate downlink interference; and sendingthe transmit power profile phase offset values to the neighboring accesspoints.
 2. The method of claim 1, further comprising: receivinginformation relating to downlink interference; and adapting the maximumand minimum power levels and/or the time period based on theinformation.
 3. The method of claim 2, wherein the information comprisesat least one downlink measurement report received from at least oneaccess terminal associated with at least one of the access points. 4.The method of claim 1, further comprising adapting the maximum andminimum power levels and/or the time period based on a quantity ofactive access terminal associated with the plurality of access pointsand/or based on downlink data traffic associated with the plurality ofaccess points.
 5. An apparatus for communication, comprising: aninterference controller configured to define a transmit power profile,define maximum and minimum power levels for the transmit power profile,and define a time period for the transmit power profile, wherein thetransmit power profile specifies how transmit power is varied over time,and wherein the transmit power profile is periodic; and a communicationcontroller configured to send at least one indication of the transmitpower profile to a plurality of access points; wherein at least aportion of the access points are neighboring access points: wherein theinterference controller is further configured to specify differenttransmit power profile phase offset values for different ones of theneighboring access points to mitigate downlink interference; and whereinthe communication controller is further configured to send the transmitpower profile phase offset values to the neighboring access points. 6.The apparatus of claim 5, wherein: the communication controller isfurther configured to receive information relating to downlinkinterference; and the interference controller is further configured toadapt the maximum and minimum power levels and/or the time period basedon the information.
 7. The apparatus of claim 6, wherein the informationcomprises at least one downlink measurement report received from atleast one access terminal associated with at least one of the accesspoints.
 8. The apparatus of claim 5, wherein the interference controlleris further configured to adapt the maximum and minimum power levelsand/or the time period based on a quantity of active access terminalassociated with the plurality of access points and/or based on downlinkdata traffic associated with the plurality of access points.
 9. Anapparatus for communication, comprising: means for defining a transmitpower profile, maximum and minimum power levels for the transmit powerprofile, and a time period for the transmit power profile, wherein thetransmit power profile specifies how transmit power is varied over time,and wherein the transmit power profile is periodic; and means forsending at least one indication of the transmit power profile to aplurality of access points; wherein at least a portion of the accesspoints are neighboring access points: wherein the means for defining isconfigured to specify different transmit power profile phase offsetvalues for different ones of the neighboring access points to mitigatedownlink interference; and wherein the means for sending is configuredto send the transmit power profile phase offset values to theneighboring access points.
 10. The apparatus of claim 9, wherein: themeans for sending is configured to receive information relating todownlink interference; and the means for defining is configured to adaptthe maximum and minimum power levels and/or the time period based on theinformation.
 11. The apparatus of claim 10, wherein the informationcomprises at least one downlink measurement report received from atleast one access terminal associated with at least one of the accesspoints.
 12. The apparatus of claim 9, wherein the means for defining isconfigured to adapt the maximum and minimum power levels and/or the timeperiod based on a quantity of active access terminal associated with theplurality of access points and/or based on downlink data trafficassociated with the plurality of access points.
 13. A computer-programproduct, comprising: a non-transitory computer-readable mediumcomprising codes for causing a computer to: define a transmit powerprofile, wherein the transmit power profile specifies how transmit poweris varied over time, and wherein the transmit power profile is periodicdefine maximum and minimum power levels for the transmit power profile;define a time period for the transmit power profile; and send at leastone indication of the transmit power profile to a plurality of accesspoints, wherein at least a portion of the access points are neighboringaccess points; specify different transmit power profile phase offsetvalues for different ones of the neighboring access points to mitigatedownlink interference; and send the transmit power profile phase offsetvalues to the neighboring access points.
 14. The computer-programproduct of claim 13, further comprising codes for causing the computerto: receive information relating to downlink interference; and adapt themaximum and minimum power levels and/or the time period based on theinformation.